DS1921H/Z High-Resolution Thermochron® iButton® Range +15°C +46°C

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DS1921H/Z High-Resolution Thermochron® iButton® Range +15°C +46°C

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19-4887; 8/09
DS1921H/Z
High-Resolution Thermochron® iButton® Range +15°C +46°C; -5°C +26°C
SPECIAL FEATURES
Digital thermometer measures temperature 1/8°C increments with ±1°C accuracy Built-in real-time clock (RTC) timer accuracy minutes month from 45°C Water resistant waterproof placed inside DS9107 iButton capsule (Exceeds Water Resistant Arequirements) Automatically wakes measures temperature user-programmable intervals from minutes Logs 2048 consecutive temperature measurements protected nonvolatile (NV) random access memory Records long-term temperature histogram with 1/2°C resolution Programmable temperature-high temperature-low alarm trip points Records time stamps durations when temperature leaves range specified trip points bytes general-purpose read/write random access memory Communicates host with single digital signal 15.4kbits 125kbits second using 1-Wire® protocol Fixed range: +15C +46°C; +26°C
Button shape self-aligning with cup-shaped probes Durable stainless steel case engraved with registration number withstands harsh environments Easily affixed with self-stick adhesive backing, latched flange, locked with ring pressed onto Presence detector acknowledges when reader first applies voltage
MICROCAN
5.89 0.51
16.25
3B2000FBC52B
Thermochron®
17.35
1-Wire
dimensions shown millimeters.
ORDERING INFORMATION
PART DS1921H-F5# DS1921Z-F5# TEMP RANGE +15C +46°C +26°C PIN-PACKAGE iButton iButton
COMMON iButton FEATURES
Digital identification information momentary contact Unique, factory-lasered tested 64-bit registration number (8-bit family code 48bit serial number 8-bit tester) assures absolute traceability because parts alike Multidrop controller 1-Wire Chip-based data carrier compactly stores information Data accessed while affixed object
#Denotes RoHS-compliant device that include lead(Pb) that exempt under RoHS requirements.
EXAMPLES ACCESSORIES
DS9096P DS9101 DS9093RA DS9093A DS9092 Self-Stick Adhesive Multi-Purpose Clip Mounting Lock Ring Snap-In iButton Probe
Thermochron, iButton, 1-Wire registered trademarks Maxim Integrated Products, Inc.
DS1921H/Z
iButton DESCRIPTION
DS1921H/Z Thermochron iButtons rugged, self-sufficient systems that measure temperature record result protected memory section. recording done user-defined rate, both direct storage temperature values well form histogram. 2048 temperature values taken equidistant intervals ranging from minutes stored. histogram provides data bins with resolution 0.5°C. temperature leaves user-programmable range, DS1921H/Z will also record when this happened, long temperature stayed outside permitted range, temperature high low. Additional bytes read/write memory allow storing information pertaining object which DS1921H/Z associated. Data transferred serially 1-Wire protocol, which requires only single data lead ground return. Every DS1921H/Z factory-lasered with guaranteed unique electrically readable 64-bit registration number that allows absolute traceability. durable stainless steel package highly resistant environmental hazards such dirt, moisture, shock. Accessories permit DS1921H/Z mounted almost object, including containers, pallets, bags.
APPLICATION
DS1921Z ideal device monitor temperature object attached shipped with, such fresh produce, medical drugs supplies. also ideal refrigerators. DS1921H intended monitoring body temperature humans animals monitoring temperature critical processes such curing, powder coating, painting. Alternatively, DS1921H used monitoring temperature clean rooms, computer equipment rooms. also calculating proportional share heating cost each party buildings with central heating. DS1921H fixed range +15C +46°C. DS1921Z fixed range +26°C. high resolution makes DS1921H DS1921Z suitable scientific research development. read/write memory store information such shipping manifests, dates manufacture, other relevant data written ASCII encrypted files. Note that initial sealing level DS1921H/Z achieves equivalent IP56. Aging conditions degrade integrity seal over time, applications with significant exposure liquids, sprays, other similar environments, recommended place Thermochron DS9107 iButton capsule. DS9107 provides watertight enclosure that been rated IP68 (refer Application Note 4126).
OVERVIEW
block diagram Figure shows relationships between major control memory sections DS1921H/Z. device seven main data components: 64-bit lasered ROM; 256-bit scratchpad; 4096-bit general-purpose SRAM; 256-bit register page timekeeping, control, counter registers; bytes alarm time stamp duration logging memory; bytes histogram memory; 2048 bytes data-logging memory. Except scratchpad, other memory arranged single linear address space. memory reserved logging purposes, counter registers several other registers read-only user. timekeeping control registers write-protected while device programmed mission. hierarchical structure 1-Wire protocol shown Figure master must first provide seven function commands: Read ROM; Match ROM; Search ROM; Conditional Search ROM; Skip ROM; Overdrive-Skip ROM; Overdrive-Match ROM. Upon completion Overdrive command byte executed standard speed, device will enter Overdrive mode, where subsequent communication occurs higher speed. protocol required these function commands described Figure After function command successfully executed, memory functions become accessible master provide
DS1921H/Z
seven available commands. protocol these memory function commands described Figure data read written least significant first.
DS1921H/Z BLOCK DIAGRAM Figure
1-Wire Port Function Control 64-Bit Lasered Parasite Powered Circuitry
Memory Function Control
256-Bit Scratchpad
General-Purpose SRAM 32.768kHz Oscillator Internal Timekeeping Control Reg. Counters
Register Page
Alarm Time Stamp Duration Logging Memory Temperature Sensor Control Logic Histogram Memory
Lithium
Datalog Memory
PARASITE POWER
block diagram (Figure shows parasite-powered circuitry. This circuitry "steals" power whenever input high. will provide sufficient power long specified timing voltage requirements met. advantages parasite power two-fold: parasiting this input, lithium conserved, lithium exhausted reason, still read normally.
64-BIT LASERED
Each DS1921 contains unique code that bits long. first eight bits 1-Wire family code. next bits unique serial number. next bits, called temperature range code, allow distinguishing DS1921H DS1921Z from each other from other DS1921 versions. last eight bits first bits. Figure details. 1-Wire generated using polynomial generator consisting shift register gates shown Figure polynomial Additional information about Maxim 1-Wire Cyclic Redundancy Check available Application Note Book iButton Standards.
DS1921H/Z
shift register bits initialized Then starting with least significant family code, time shifted After eighth family code been entered, then serial number followed temperature range code entered. After range code been entered, shift register contains value. Shifting eight bits returns shift register
HIERARCHICAL STRUCTURE 1-Wire PROTOCOL Figure
Master 1-Wire Other Devices
DS1921 Command Level: Available Commands:
Read Match Search Skip Overdrive Skip Overdrive Match Conditional Search Write Scratchpad Read Scratchpad Copy Scratchpad Read Memory Read Memory w/CRC Clear Memory
Cmd. Data Field Codes: Affected:
64-bit Reg. 64-bit Reg. 64-bit Reg. OD-Flag 64-bit Reg. OD-Flag 64-bit Reg. Cond. Search settings, device status 256-bit scratchpad, flags 256-bit scratchpad 4096-bit SRAM, registers, flags memory memory Mission Time Stamp, Mission Samples Counter, Start Delay, Sample Rate, Alarm Time Stamps Durations, Histogram Memory Memory address 211h
1-Wire Function Commands
DS1921-Specific Memory/Control Function Commands
Convert Temperature
64-BIT LASERED Figure
8-Bit Code DEVICE DS1921H-F5 DS1921Z-F5 12-Bit Temperature Range Code TEMP. RANGE (°C) 36-Bit Serial Number TEMP. RANGE CODE 0100 0011 1111 1011 0010 0010 8-Bit Family Code (21h)
RESOLUTION 0.125 0.125
HEX. EQUIVALENT
DS1921H/Z
1-Wire GENERATOR Figure
Polynomial
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
INPUT DATA
MEMORY
memory DS1921H/Z shown Figure 4096-bit general-purpose SRAM make pages through timekeeping, control, counter registers fill page called Register Page (see Figure Pages assigned storing alarm time stamps durations. temperature histogram bins begin page four pages. temperature logging memory covers pages 191. Memory pages 127, reserved future extensions. scratchpad additional page that acts buffer when writing SRAM memory register page. memory pages higher read-only user. They written erased solely under supervision on-chip control logic.
DS1921H/Z MEMORY Figure
32-Byte Intermediate Storage Scratchpad ADDRESS 0000h 01FFh 0200h 021Fh 0220h 027Fh 0280h 07FFh 0800h 087Fh 0880h 0FFFh 1000h 17FFh 1800h 1FFFh General-Purpose SRAM Pages) 32-Byte Register Page Alarm Time Stamps Durations (Reserved Future Extensions) Temperature Histogram Memory (Reserved Future Extensions) Datalog Memory Pages) (Reserved Future Extensions) Pages Page Pages Pages Pages Pages Pages Pages
DS1921H/Z
DS1921H/Z REGISTER PAGE Figure
ADDR 0200h 0201h 0202h 0203h 0204h 0205h 0206h 0207h 0208h 0209h 020Ah 020Bh 020Ch 020Dh 020Eh 020Fh 0210h 0211h 0212h 0213h 0214h 0215h 0216h 0217h 0218h 0219h 021Ah 021Bh 021Ch 021Dh 021Eh 021Fh CENT Seconds Minutes 10h. 12/24 20h.
AM/PM
Single Seconds Single Minutes Single Hours
Function RealTime Clock Registers
Access*
R/W; R/W**
Week Date Single Date 10m. Single Months Years Single Years Seconds Alarm Single Seconds Alarm Minutes Alarm Single Minutes Alarm 12/24 10ha. 10h. Single Hours Alarm alm. Week Alarm Temperature Alarm Threshold Temperature High Alarm Threshold Number Minutes Between Temperature Conversions
EMCLR
RealTime Clock Alarm Registers Temp. Alarms
Sample Rate
R/W; R/W**
R/W; R/W**
R/W;
R/W; R/W**
EOSC
function, reads 00h) function, reads 00h) Temperature Read (Forced Conversion) Byte High Byte MEMCLR Minutes Hours Date Month Year Byte Center Byte High Byte Byte Center Byte High Byte
Control (N/A) (N/A) Temp. Start Delay Status Mission Time Stamp Mission Samples Counter Device Samples Counter
R/W; R/W**
R/W;
*The first entry column ACCESS valid between missions. second entry shows applicable access mode while mission progress. **While mission progress, these addresses read. first attempt write these registers (even read-only ones), however, will mission overwrite selected writeable registers.
TIMEKEEPING
RTC/alarm calendar information accessed reading/writing appropriate bytes register page, address 200h 206h. Note that some bits These bits will always read regardless they written. contents time, calendar, alarm registers Binary-Coded Decimal (BCD) format.
DS1921H/Z
Alarm Register Bitmap
ADDR 0200h 0201h 0202h 0203h 0204h 0205h 0206h 0207h 0208h 0209h 020Ah CENT Seconds Minutes 10h. 12/24 20h.
AM/PM
Single Seconds Single Minutes Single Hours
Date 10m. Years Seconds Alarm Minutes Alarm 12/24 10ha. 10h. alm.
Week Single Date Single Months Single Years Single Seconds Alarm Single Minutes Alarm Single Hours Alarm
Week Alarm
RTC/Calendar
DS1921H/Z either 12-hour 24-hour mode. Hours Register (address 202h) defined 24-hour mode select bit. When high, 12-hour mode selected. 12-hour mode, AM/PM with logic being 24-hour mode, 20hour hours). distinguish between days week DS1921H/Z includes counter with range from assignment counter value week arbitrary. Typically, number assigned Sunday (U.S. standard) Monday (European standard). calendar logic designed automatically compensate leap years. every year value that either multiple device will 29th February. This will work correctly (but including) year 2100. DS1921H/Z Y2K-compliant. (CENT) Months Register address 205h serves century flag. When Year Register rolls over from century flag will toggle. recommended write century when setting time/date between years 2000 2099.
Alarms
DS1921H/Z also contains alarm function. alarm registers located registers 207h 20Ah. most significant each alarm registers mask bit. When mask bits logic alarm will occur once week when values stored timekeeping registers 200h 203h match values stored time alarm registers. alarm will Timer Alarm Flag (TAF) device's Status Register (address 214h). master Search Conditions Control Register (address 20Eh) identify devices with timer alarms means Conditional Search function (see Function Commands).
DS1921H/Z
Alarm Control
ALARM REGISTER MASK BITS (Bit 207h 20Ah) Alarm once second. Alarm when seconds match (once minute). Alarm when minutes seconds match (once every hour). Alarm when hours, minutes seconds match (once every day). Alarm when day, hours, minutes, seconds match (once every week).
TEMPERATURE CONVERSION
DS1921H DS1921Z measure temperatures with resolution 1/8th degree Celsius. Temperature values represented single byte unsigned binary number, which translates into range 32°C. possible values 0000 0000 (00h) through 1111 1111 (FFh). codes considered valid temperature readings. Since DS1921H DS1921Z have different starting temperatures, meaning binary temperature code depends device. temperature conversion yields temperature that out-of-range, will recorded low) high). Since out-of-range results accumulated histogram bins data these bins limited value (see Temperature Logging Histogram section). this reason specified temperature range DS1921H DS1921Z considered begin code code FBh, which corresponds histogram bins With T[7.0] representing decimal equivalent temperature reading, temperature value calculated (°C) T[7.0] 14.500 (DS1921H) (°C) T[7.0] 5.500 (DS1921Z) This equation valid converting temperature readings stored datalog memory well data read from forced temperature conversion readout Register (address 211h). specify high temperature alarm thresholds, this equation needs resolved T[7.0] (°C) -116 (DS1921H) T[7.0] (°C) (DS1921Z) value 23°C, example, thus translates into decimal DS1921H, decimal DS1921Z. This corresponds binary patterns 0100 0100 1110 0100 respectively, which could written Temperature Alarm Register (address 020Bh 020Ch, respectively).
Temperature Alarm Register
ADDR 020Bh 020Ch Temperature Alarm Threshold Temperature High Alarm Threshold
DS1921H/Z
SAMPLE RATE
content Sample Rate Register (address 020Dh) determines many minutes temperature conversions apart from each other during mission. sample rate value from 255, coded unsigned 8-bit binary number. memory been cleared (Status Register MEMCLR mission enabled (Status Register writing non-zero value Sample Rate Register will start mission. full description correct sequence steps start temperaturelogging mission sections Missioning Missioning Example.
Sample Rate Register
ADDR 020Dh Sample Rate
CONTROL REGISTER
DS1921H/Z operation writing appropriate data special function registers that located register page. Several functions that controlled single only combined into single byte called Control Register (address 20Eh). This register read written. device programmed mission, writing Control Register will mission change register contents.
Control Register Bitmap
ADDR 020Eh EOSC
EMCLR
functional assignments individual bits explained table below. function. always reads cannot written
Control Register Details
DESCRIPTION EOSC: Enable Oscillator BIT(S) DEFINITION This controls crystal oscillator RTC. When logic oscillator will start operation. When written logic oscillator will stop device low-power data retention mode. This must normal operation. must have advanced least second before mission start will accepted. This needs logic enable Clear Memory function, which invoked memory function command. Time-Stamp, Histogram Memory well Mission Time Stamp, Mission Samples Counter, Mission Start Delay Sample Rate will cleared only Clear Memory command issued with next access device. EMCLR will return next memory function command executed. This controls whether DS1921H/Z will begin mission soon sample rate written. enable device mission, this must This controls whether temperature logging memory overwritten with data whether data logging stopped once memory filled with data during mission. Setting this enables rollover data logging continues beginning overwriting previously collected data. Clearing this disables rollover further temperature values will stored temperature logging memory once filled with data. This will stop mission. device will continue measuring temperatures updating histogram alarm time stamps durations.
EMCLR: Memory Clear Enable
Enable Mission Rollover Enable/Disable
DESCRIPTION TLS: Temperature Alarm Search THS: Temperature High Alarm Search TAS: Timer Alarm Search
BIT(S)
DS1921H/Z DEFINITION this device will respond Conditional Search command during mission temperature reached lower than Temperature Threshold stored address 020Bh. this device will respond Conditional Search command during mission temperature reached higher than High Temperature Threshold stored address 020Ch. this device will respond Conditional Search command during mission timer alarm occurred. Since timer alarm cannot disabled, flag usually reads during mission. Therefore advisable most cases.
Mission Start Delay Counter
content Mission Start Delay Counter determines many minutes device will wait before starting logging process. mission start delay value stored unsigned 16-bit integer number addresses 212h (low byte) 213h (high byte). maximum delay 65535 minutes, equivalent days, hours, minutes. typical mission, Mission Start Delay mission long single DS1921H/Z store temperature readings selected sample rate, several devices, staggering Mission Start Delay record full period. this case, control register (address 020Eh) must prevent overwriting recorded temperature after datalog memory full. Mission Start Logging Process description flow chart details.
Status Register
Status Register holds device status information alarm flags. register located address 214h. Writing this register will necessarily mission.
Status Register Bitmap
ADDR 0214h
MEMCLR
functional assignments individual bits explained table below. bits MIP, TLF, only written other bits read-only. function.
Status Register Details
DESCRIPTION TCB: Temperature Core Busy BIT(S) DEFINITION this reads DS1921H/Z currently performing temperature conversion, either self-initiated because mission being progress initiated command when mission progress. goes just before conversion starts returns high just after result latched into readout register address 0211h. this reads memory pages higher (alarm time stamps/durations, temperature histogram, excluding datalog memory), well Mission Time Stamp, Mission Samples Counter, Mission Start Delay Sample Rate have been cleared from executing Clear Memory function command. MEMCLR will return soon writing non-0 value Sample Rate Register starts mission, provided that also memory cleared order mission start.
MEMCLR: Memory Cleared
DESCRIPTION MIP: Mission Progress
BIT(S)
SIP: Sample Progress
TLF: Temperature Flag
THF: Temperature High Flag
TAF: Timer Alarm Flag
DS1921H/Z DEFINITION this reads DS1921H/Z been mission this mission still progress. mission started Control Register (address 20Eh) non-zero value written Sample Rate Register, address 20Dh. returns from logic logic when mission ended. mission will with first write attempt (Copy Scratchpad command) register address range 200h 213h. Alternatively, mission ended directly writing Status Register setting cannot writing status register. this reads DS1921H/Z currently performing temperature conversion part mission progress. mission samples occur seconds rollover from will change from approximately 250ms before actual temperature conversion begins allowing circuitry chip wake-up. temperature conversion including wake-up phase takes maximum 875ms. During this time read accesses memory pages higher permissible reveal invalid data. Logic Temperature Flag indicates that temperature measurement during mission revealed temperature equal lower than value Temperature Threshold Register. Temperature Flag cleared time writing this This flag must cleared before starting mission. Logic Temperature High Flag indicates that temperature measurement during mission revealed temperature equal higher than value Temperature High Threshold Register. Temperature High Flag cleared time writing this This flag must cleared before starting mission. this reads alarm occurred (see section TIMEKEEPING details). Timer Alarm Flag cleared time writing this logic Since timer alarm cannot disabled, flag usually reads during mission. This flag should cleared before starting mission.
MISSION TIME STAMP
Mission Time Stamp indicates time date first temperature conversion mission. Subsequent temperature conversions will take place many minutes apart from each other specified value Sample Rate Register. Mission samples occur minute boundaries.
Mission Time Stamp Register Bitmap
ADDR 0215h 0216h 0217h 0218h 0219h 12/24 Minutes
20h. AM/PM
10h.
Single Minutes Single Hours Single Date Single Months Single Years
Date 10m. Years
MISSION SAMPLES COUNTER
Mission Samples Counter indicates many temperature measurements have taken place during current mission progress during latest mission value stored unsigned 24-bit integer number. This counter reset through Clear Memory command.
DS1921H/Z
Mission Samples Counter Register
ADDR 021Ah 021Bh 021Ch Byte Center Byte High Byte
DEVICE SAMPLES COUNTER
Device Samples Counter indicates many temperature measurements have taken place since device assembled factory. value stored unsigned 24-bit integer number. maximum number that represented this format 16777215, which higher than expected lifetime DS1921H/Z iButton. This counter cannot reset under software control.
Device Samples Counter Register
ADDR 021Dh 021Eh 021Fh Byte Center Byte High Byte
TEMPERATURE LOGGING HISTOGRAM
Once setup mission, DS1921H/Z logs temperature measurements simultaneously byte after byte datalog memory well histogram form histogram memory. datalog memory able store 2048 temperature values measured equidistant time points. first temperature value mission written address location 1000h datalog memory, second value address location 1001h Knowing starting time point (Mission Time Stamp), interval between temperature measurements, Mission Samples Counter, rollover setting, reconstruct time date each measurement stored datalog. There alternatives DS1921H/Z will behave after 2048 bytes datalog memory filled with data. With rollover disabled device will fill datalog memory with first 2048 mission samples. Additional mission samples logged datalog, histogram, temperature alarm memory continue update. With rollover enabled datalog will wrap around, overwrite previous data starting 1000h every 2049th mission sample. this mode device stores last 2048 mission samples. temperature histogram, DS1921H/Z provides bins that begin memory address 0800h. Each consists 16-bit, non-rolling-over binary counter that incremented each time temperature value acquired during mission falls into range bin. least significant byte each stored lower address. begins memory address 0800h, 0802h, 087Eh shown Figure number updated after temperature conversion determined cutting least significant bits binary temperature value. range values range locked counted FFh.
DS1921H/Z
HISTOGRAM TEMPERATURE CROSS-REFERENCE Figure
TEMPERATURE READING DS1921H TEMP. EQUIV. 14.500 14.625 14.750 14.875 15.000 15.125 15.250 15.375 15.500 45.375 45.500 45.625 45.750 45.875 46.000 46.125 46.250 46.375 DS1921Z TEMP. EQUIV. -5.500 -5.375 -5.250 -5.125 -5.000 -4.875 -4.750 -4.625 -4.500 25.375 25.500 25.625 25.750 25.875 26.000 26.125 26.250 26.375 HISTOGRAM NUMBER HISTOGRAM ADDRESS 800h 801h 800h 801h 800h 801h 800h 801h 802h 803h 802h 803h 802h 803h 802h 803h 804h 805h 87Ah 87Bh 87Ch 87Dh 87Ch 87Dh 87Ch 87Dh 87Ch 87Dh 87Eh 87Fh 87Eh 87Fh 87Eh 87Fh 87Eh 87Fh
Since each data bytes increment 65535 times. Additional measurements that already reached maximum value will counted; counter will remain maximum value. With fastest sample rate sample every minute, 2-byte sufficient days temperature readings fall into same bin.
TEMPERATURE ALARM LOGGING
some applications essential only record temperature over time temperature histogram, also record when exactly temperature exceeded predefined tolerance band long temperature stayed outside desirable range. DS1921H/Z high durations. tolerance band specified means Temperature Alarm Threshold Registers, addresses 20Bh 20Ch register page. high temperature threshold. section Temperature Conversion data format temperature written long temperature values stay within tolerance band (i.e., higher than threshold lower than high threshold), DS1921H/Z will record temperature alarm. temperature during mission reaches exceeds either threshold, DS1921H/Z will generate alarm either Temperature High Flag (THF) Temperature Flag (TLF) Status Register (address 214h). This way, search conditions (address 20Eh) accordingly, master quickly identify devices with temperature alarms means Conditional Search function (see Function Commands). device also generates time stamp when alarm occurred begins recording duration alarming temperature. Time stamps durations where temperature leaves tolerance band stored address range 0220h 027Fh, shown Figure This allocation allows recording individual alarm events
DS1921H/Z
periods periods cold). date time each these periods determined from Mission Time Stamp time distance between each temperature reading.
ALARM TIME STAMPS DURATIONS ADDRESS Figure
ADDRESS 0220h 0221h 0222h 0223h 0224h 0227h 0228h 024Fh 0250h 0251h 0252h 0253h 0254h 0257h 0258h 027Fh DESCRIPTION Mission Samples Counter Byte Mission Samples Counter Center Byte Mission Samples Counter High Byte Alarm Duration Counter Alarm Time Stamp Duration Alarm Time Stamp Durations Mission Samples Counter Byte Mission Samples Counter Center Byte Mission Samples Counter High Byte Alarm Duration Counter Alarm Time Stamp Duration Alarm Time Stamp Durations High Alarm High Alarms High Alarm Alarm Alarms Alarm ALARM EVENT
alarm time stamp copy Mission Samples Counter when alarm first occurred. least significant byte stored lower address. address higher than time stamp DS1921H/Z maintains 1-byte duration counter that stores number samples temperature found beyond threshold. this counter reached limit after consecutive temperature readings temperature returned within tolerance band, device will issue another time stamp next higher alarm location open another counter record duration. temperature returns normal before counter reached limit, duration counter particular time stamp will increment further. Should temperature again cross this threshold, will recorded next available alarm location. This algorithm implemented well high temperature threshold.
MISSIONING
typical task DS1921H/Z recording temperature temperature-sensitive object. Before device perform this function, needs configured. This procedure called missioning. First all, DS1921H/Z needs have valid time date. This reference time (also called GMT, Greenwich Mean Time) other time standard that chosen application. clock must running (EOSC least second. Setting alarm optional. memory assigned storing alarm time stamps durations, temperature histogram, well Mission Time Stamp, Mission Samples Counter, Mission Start Delay, Sample Rate must cleared using Memory Clear command. case there were temperature alarms previous mission, flags need cleared manually. enable device mission, flag must These general settings that have made regardless type object monitored duration mission. Next, temperature high temperature thresholds specify temperature tolerance band must defined. convert temperature value into binary code written threshold registers described under Temperature Conversion earlier this document.
DS1921H/Z
state Search Condition bits Control Register does affect mission. multiple devices connected form 1-Wire net, setting search condition will enable devices participate conditional search certain events such timer temperature alarm have occurred. Details search conditions found section Function Commands later this document Control Register description. setting (rollover enable) sample rate depends duration mission monitoring requirements. most recent temperature history important, rollover should enabled Otherwise, should estimate duration mission minutes divide number 2048 calculate value sample rate (number minutes between temperature conversions). estimated duration mission days 14400 minutes) example, then 2048-byte capacity datalog memory would sufficient store value every minutes. datalog memory DS1921H/Z large enough store temperature readings, several devices Mission Start Delay values that make second device start recording soon memory first device full, RO-bit needs disable rollover that would otherwise overwrite recorded temperature log. After Mission Start Delay set, Sample Rate Register last element data that written. sample rate value from 255, coded unsigned 8-bit binary number. soon sample rate written, DS1921H/Z will flag clear MEMCLR flag. After many minutes specified Mission Start Delay over, device will wait next minute boundary, then wake copy current time date Mission Time Stamp Register, make first temperature conversion mission. This increments both Mission Samples Counter Device Samples Counter. subsequent temperature measurements taken minute boundaries specified value Sample Rate Register. read memory DS1921H/Z watch mission progresses. Care should taken avoid memory access conflicts. section Memory Access Conflicts details.
MEMORY/CONTROL FUNCTION COMMANDS
Memory/Control Function Flow Chart (Figure describes protocols necessary accessing memory special function registers DS1921H/Z. example these other functions DS1921H/Z mission included this document, preceding Electrical Characteristics section. communication between master DS1921H/Z takes place either regular speed (default, Overdrive Speed explicitly into Overdrive mode, DS1921H/Z assumes regular speed. Internal memory access during mission priority over external access through 1-Wire interface. This affect Read Memory commands described below. section Memory Access Conflicts details.
ADDRESS REGISTERS TRANSFER STATUS
Because serial data transfer, DS1921H/Z employs three address registers, called TA1, TA2, (Figure Registers must loaded with target address which data will written from which data will sent master upon Read command. Register acts like byte counter transfer status register. used verify data integrity with Write commands. Therefore, master only read access this register. lower bits Register indicate address last byte that been written scratchpad. This address called Ending Offset. Register, called "partial byte flag," number data bits sent master integer multiple always Note that lowest bits target address also determine address within scratchpad, where intermediate storage data will begin. This address called
DS1921H/Z
byte offset. target address Write command 13Ch, example, then scratchpad will store incoming data beginning byte offset will full after only bytes. corresponding ending offset this example 1Fh. best economy speed efficiency, target address writing should point beginning page, (i.e., byte offset will Thus, full 32-byte capacity scratchpad available, resulting also ending offset 1Fh. However, possible write several contiguous bytes somewhere within page. ending offset together with Partial Overflow Flag mainly means support master checking data integrity after Write command. highest valued Register, called Authorization Accepted, indicates that valid copy command scratchpad been received executed. Writing data scratchpad clears this flag.
ADDRESS REGISTERS Figure
Target Address (TA1)
Target Address (TA2) Ending Address with Data Status (E/S) (Read Only)
WRITING WITH VERIFICATION
write data DS1921H/Z, scratchpad used intermediate storage. First, master issues Write Scratchpad command specify desired target address, followed data written scratchpad. next step, master sends Read Scratchpad command read scratchpad verify data integrity. preamble scratchpad data, DS1921H/Z sends requested target address contents Register. flag set, data arrive correctly scratchpad. master does need continue reading; start trial write data scratchpad. Similarly, flag indicates that Write command recognized device. everything went correctly, both flags cleared ending offset indicates address last byte written scratchpad. master continue verifying every data bit. After master verified data, send Copy Scratchpad command. This command must followed exactly data three address registers TA1, master read them verifying scratchpad. soon DS1921H/Z received these bytes, will copy data requested location beginning target address.
Write Scratchpad Command [0Fh]
After issuing Write Scratchpad command, master must first provide 2-byte target address, followed data written scratchpad. data will written scratchpad starting byte offset (T4:T0). ending offset (E4:E0) will byte offset which master stops writing data. Only full data bytes accepted. last data byte incomplete, content will ignored partial byte flag (PF) will set. When executing Write Scratchpad command, generator inside DS1921H/Z (see Figure calculates entire data stream, starting command code ending last data
DS1921H/Z
byte sent master. This generated using CRC16 polynomial first clearing generator then shifting command code (0Fh) Write Scratchpad command, Target Addresses supplied master data bytes. master Write Scratchpad command time. However, ending offset 11111b, master send read time slots will receive inverted CRC16 generated DS1921H/Z. range 200h 213h register page protected during mission. Figure Register Page Map, access type individual registers between during missions.
Read Scratchpad Command [AAh]
This command used verify scratchpad data target address. After issuing Read Scratchpad command, master begins reading. first bytes will target address. next byte will ending offset/data status byte (E/S) followed scratchpad data beginning byte offset (T4:T0), shown Figure Regardless actual ending offset, master read data until scratchpad after which will receive inverted CRC16 command code, Target Addresses TA2, byte, scratchpad data starting target address. After read, master will read logical from DS1921H/Z until reset pulse issued.
Copy Scratchpad [55h]
This command used copy data from scratchpad writable memory sections. Applying Copy Scratchpad Sample Rate Register start mission provided that several preconditions met. Mission Start Logging Process description flow chart Figure details. After issuing Copy Scratchpad command, master must provide 3-byte authorization pattern, which obtained reading scratchpad verification. This pattern must exactly match data contained three address registers (TA1, TA2, E/S, that order). pattern matches, (Authorization Accepted) flag will copy will begin. pattern alternating will transmitted after data been copied until master issues reset pulse. While copy progress attempt reset part will ignored. Copy typically takes byte. data copied determined three address registers. scratchpad data from beginning offset through ending offset will copied, starting target address. Anywhere from bytes copied memory with this command. flag will remain logic until cleared next Write Scratchpad command. Note that Copy Scratchpad when applied address range 200h 213h during mission will mission.
Read Memory [F0h]
Read Memory command used read entire memory. After issuing command, master must provide 2-byte target address. After bytes, master reads data beginning from target address continue until memory, which point logic will read. important realize that target address registers will contain address provided. ending offset/data status byte unaffected. hardware DS1921H/Z provides means accomplish error-free writing memory section. safeguard data 1-Wire environment when reading simultaneously speed data transfers, recommended packetize data into data packets size memory page each. Such packet would typically store 16-bit with each page data ensure rapid, error-free data transfers that eliminate having read page multiple times verify whether received data correct. (See Application Note recommended file structure.)
DS1921H/Z
MEMORY/CONTROL FUNCTION FLOW CHART Figure 10-1
Master Memory Control Fkt. Command Write Scratchpad DS1921 sets EMCLR Master (T7:T0), (T15:T8) DS1921 sets Scratchpad Offset (T4:T0) Clears (PF, Master Data Byte Scratchpad Offset DS1921 sets (E4:E0) Scratchpad Offset DS1921 Increments Scratchpad Offset From Functions Flow Chart (Figure Read Scratchpad DS1921 sets EMCLR Master (T7:T0), (T15:T8) Master Ending Offset with Data Status (E/S) DS1921 sets Scratchpad Offset (T4:T0) Master Data Byte from Scratchpad Offset Figure Part
Master Reset? DS1921 Increments Scratchpad Offset Scratchpad Offset 11111b? Master Reset?
Master Reset? Scratchpad Offset 11111b?
Partial Byte Written?
Master CRC16 Command, Address Data, Byte, Data Starting Target Address
Master CRC16 Command, Address, Data
Master Reset? Master "1"s
Master Reset? Master "1"s
Functions Flow Chart (Figure
From Figure Part
DS1921H/Z
MEMORY/CONTROL FUNCTION FLOW CHART Figure 10-2
From Figure Part
Copy Scratchpad DS1921 sets EMCLR Master (T7:T0), (T15:T8) Master Byte
Read Memory DS1921 sets EMCLR
Figure Part
Master (T7:T0), (T15:T8) DS1921 sets Memory Address (T15:T0) DS1921 Increments Address Counter Master Reset? Master Data Byte from Memory Address
Authorization Code Match?
DS1921 Copies Scratchpad Data Memory
Master "1"s Copying Finished DS1921
Master "1"s
Memory?
Master Reset?
Master "0"s
Master Reset? DS1921
Master Reset?
Figure Part
From Figure Part
DS1921H/Z
MEMORY/CONTROL FUNCTION FLOW CHART Figure 10-3
From Figure Part
Read Mem. w/CRC DS1921 sets EMCLR Master (T7:T0), (T15:T8) DS1921 sets Memory Address (T15:T0)
Figure Part
Decision made DS1921
Decision made Master Master Byte
Memory? Master Data Byte from Memory Address DS1921 Increments Address Counter
Master Reset? Page? Master CRC16 Command, Address, Data (1st Pass); CRC16 Data (Subsequent Passes) Master Reset
Figure Part
From Figure Part
DS1921H/Z
MEMORY/CONTROL FUNCTION FLOW CHART Figure 10-4
From Figure Part
Clear Memory
Convert Temp. DS1921 sets EMCLR
EMCLR DS1921 clears Mission Time Stamp, Mission Samples Counter, Mission Start Delay, Sample Rate Register DS1921 clears Alarm Time Stamps Durations DS1921 clears Histogram Memory DS1921 sets MEMCLR DS1921 sets EMCLR
Mission Progress?
Temperature Conversion Process DS1921 sets TCB\ DS1921 Performs Temp. Conversion DS1921 copies Result Address 0211h DS1921 sets TCB\ Process
DS1921 Starts Temperature Conversion Process
Master Reset?
Master Reset? Master Reset?
Figure Part
DS1921H/Z
Read Memory with [A5h]
Read Memory with command used read memory data that cannot packetized, such register page data recorded device during mission. command works essentially same simple Read Memory, except 16-bit that DS1921H/Z generates transmits following last data byte memory page. After having sent command code Read Memory with command, master sends 2byte address (TA1 T7:T0, T15:T8) that indicates starting byte location. With subsequent read data time slots master receives data from DS1921H/Z starting initial address continuing until 32-byte page reached. that point master will send additional read data time slots receive inverted 16-bit CRC. With subsequent read data time slots master will receive data starting beginning next page followed again inverted that page. This sequence will continue until master resets device. With initial pass through Read Memory with flow, 16-bit value result shifting command byte into cleared generator followed address bytes contents data memory. Subsequent passes through Read Memory with flow will generate 16-bit that result clearing generator then shifting contents data memory page. After 16-bit last page read, master will receive logical from DS1921H/Z inverted CRC16s page boundaries until reset pulse issued. Read Memory with command sequence ended point issuing reset pulse.
Clear Memory [3Ch]
Clear Memory command used clear Sample Rate, Mission Start Delay, Mission Time Stamp, Mission Samples Counter register page Temperature Alarm Memory Temperature Histogram Memory. These memory areas must cleared device another mission. Clear Memory command does clear datalog memory temperature timer alarm flags Status Register. oscillator must have counted least second, before issuing command. Clear Memory command function EMCLR Control Register must Clear Memory command must issued with very next access device's memory functions. Issuing other memory function command will reset EMCLR bit. Clear Memory process takes 500µs. When command completed MEMCLR Status Register will read EMCLR will
Convert Temperature [44h]
mission progress (MIP Convert Temperature command issued measure current temperature device. result temperature conversion will found memory address 211h register page. This command takes maximum 360ms complete. During this time device remains fully accessible memory/control function commands.
DS1921H/Z
Mission Start Logging Process
DS1921H/Z does special command start mission. Instead, mission started writing non-zero value Sample Rate Register using Copy Scratchpad command. shown Figure mission only started previous mission been stopped (MIP memory cleared (MEMCLR mission enabled sample rate different from zero, value will copied sample rate register. same time will MEMCLR will cleared indicate that device mission. Next Mission Start Delay counter will start decrementing every minute until down DS1921H/Z will wait until next minute boundary start logging process, which first action copies applicable registers Mission Time Stamp.
MISSION START LOGGING PROCESS Figure
Mission Start Process invoked when Copy Scratchpad function used sample rate writing Sample Rate Register address 020Dh. minute after start delay countdown over, Logging Process begins Mission Start Process ends.
Mission Start Process DS1921 Sets Logging Process DS1921 Copies Mission Time Stamp DS1921 sets Datalog Address 1000h DS1921 Measures Temperature DS1921 Updates Histogram, Device Samples Counter, Mission Samples Counter Alarm, applicable
MEMCLR Sample Rate DS1921 Copies Sample Rate from Scratchpad Sample Rate Register DS1921 sets MEMCLR
Datalog Address 1800h? DS1921 Stores Temp. Datalog Address DS1921 Increments Datalog Address DS1921 Stores Temp. Datalog Address DS1921 Increments lower bits Datalog Address
Start Delay Counter DS1921 Waits Until Next Minute Boundary DS1921 Decrements Start Delay Counter
DS1921 Waits Until Next Minute Boundary DS1921 Logging Process
DS1921 Waits Sample Period
Process
Process
DS1921H/Z
Stop Mission
DS1921H/Z does have special command stop mission. mission stopped time writing address range 0200h 0213h writing Status Register address 0214h Either approach involves Copy Scratchpad command. There need Mission Start Delay expire before mission stopped (see Figure 11).
MEMORY ACCESS CONFLICTS
While mission progress, periodically temperature sample taken stored datalog, histogram, potentially alarm memory. This "internal activity" priority over Read Memory Read Memory with access these pages. conflict occurs, data read invalid, even value matches data. ensure that data read valid, recommended first read Status Register. set, delay reading datalog, histogram, alarm memory until interference more likely seen with high sample rate sample every minute). Since mission samples occur seconds rollover 00), memory conflicts avoided first reading seconds counter. example, takes seconds read datalog, then avoid starting memory read seconds counter Alternatively, read affected memory section twice accept data only both readings match. case, when writing driver software, important know about possibility interference take measures work around
1-WIRE SYSTEM
1-Wire system that single master more slaves. instances DS1921H/Z slave device. master typically microcontroller. discussion this system broken down into three topics: hardware configuration, transaction sequence, 1-Wire signaling (signal types timing). 1-Wire protocol defines transactions terms state during specific time slots that initiated falling edge sync pulses from master. more detailed protocol description, refer Chapter Book DS19xx iButton Standards.
HARDWARE CONFIGURATION
1-Wire only single line definition; important that each device able drive appropriate time. facilitate this, each device attached 1-Wire must have open drain tri-state outputs. 1-Wire port DS1921H/Z open-drain with internal circuit equivalent that shown Figure multidrop consists 1-Wire with multiple slaves attached. standard speed 1-Wire maximum data rate 16.3kbits second. speed boosted 142kbits second activating Overdrive mode. DS1921H/Z guaranteed fully compliant iButton Standard. maximum data rate standard speed mode 15.4kbits second 125kbits second Overdrive. value pull-up resistor primarily depends network size load conditions. DS1921H/Z requires pull-up resistor maximum 2.2k speed. idle state 1-Wire high. reason transaction needs suspended, must left idle state transaction resume. this does occur left more than 16µs (Overdrive speed) more than 120µs (standard speed), more devices reset. Note that DS1921H/Z does quite meet full 16µs maximum time normal 1-Wire Overdrive timing. With DS1921H/Z must left longer than 15µs Overdrive speed ensure that DS1921H/Z 1-Wire performs reset. DS1921H/Z will communicate properly when used conjunction with DS2480B DS2490 1-Wire driver adapters that based these driver chips.
DS1921H/Z
HARDWARE CONFIGURATION Figure
MASTER VPUP RPUP DATA Typ. MOSFET DS1921 1-Wire PORT
Open Drain Port
RECEIVE TRANSMIT
TRANSACTION SEQUENCE
protocol accessing DS1921H/Z 1-Wire port follows: Initialization Function Command Memory/Control Function Command Transaction/Data
INITIALIZATION
transactions 1-Wire begin with initialization sequence. initialization sequence consists reset pulse transmitted master followed presence pulse(s) transmitted slave(s).The presence pulse lets master know that DS1921H/Z ready operate. more details, 1-Wire Signaling section.
FUNCTION COMMANDS
Once master detected presence, issue seven function commands. function commands eight bits long. list these commands follows (refer flowchart Figure 13).
Read [33h]
This command allows master read DS1921H/Z's 8-bit family code, temperature range code, plus unique 36-bit serial number 8-bit CRC. This command only used there single slave bus. more than slave present bus, data collision will occur when slaves transmit same time (open drain will produce wired-AND result). resultant family code temperature range code plus 36-bit serial number will result mismatch CRC.
Match [55h]
Match command, followed 64-bit sequence, allows master address specific DS1921H/Z multidrop bus. Only DS1921H/Z that exactly matches 64-bit sequence will respond following memory function command. other slaves will wait reset pulse. This command used with single multiple devices bus.
DS1921H/Z
Search [F0h]
When system initially brought master might know number devices 1Wire their registration numbers. taking advantage wired-AND property bus, master process elimination identify registration numbers slave devices. each registration number, starting with least significant bit, master issues triplet time slots. first slot, each slave device participating search outputs true value registration number bit. second slot, each slave device participating search outputs complemented value registration number bit. third slot, master writes true value selected. slave devices that match written master stop participating search. both read bits zero, master knows that slave devices exist with both states bit. choosing which state write, master branches romcode tree. After complete pass, master knows registration number single device. Additional passes identify registration numbers remaining devices. Refer Note 187: 1-Wire Search Algorithm detailed discussion, including example.
Conditional Search [ECh]
Conditional Search command operates similarly Search command except that only devices fulfilling specified condition will participate search. condition specified functions TAS, THS, Control Register, address 20Eh. Conditional Search provides efficient means master determine devices multidrop system that have signal important event, such temperature leaving tolerance band. After each pass conditional search that successfully determined 64-bit code specific device multidrop bus, that particular device individually accessed Match been issued, since other devices will have dropped search process will waiting reset pulse. conditional search, select combination three search conditions writing associated logical These bits correspond directly flags Status Register device. flag status register reads corresponding Control Register logical too, device will respond Conditional Search command. more than search condition selected, first event occurring will make device respond Conditional Search command.
Skip [CCh]
This command save time single-drop system allowing master access memory functions without providing 64-bit code. more than slave present and, example, Read command issued following Skip command, data collision will occur multiple slaves transmit simultaneously (open drain pull-downs will produce wired-AND result).
DS1921H/Z
FUNCTIONS FLOW CHART Figure 13-1
From Memory Functions Flow Chart (Figure Master Reset Pulse From Figure Part
Short Reset Pulse? DS1921 Presence Pulse Master Function Command
Read ROM?
Match ROM?
Search ROM?
Cond. Search ROM? Cond. Met? DS1921 DS1921 Master Match? DS1921 DS1921 Master Match? DS1921 DS1921 Master Match?
Figure Part
DS1921 Family Code Byte
Master
DS1921 DS1921 Master Match? Match? DS1921 Master DS1921 Master Match? Match?
DS1921 Temp. Range Code Serial Number Bytes
DS1921 Byte
Master
DS1921 DS1921 Master Match? Match?
Figure Part
transmitted received Overdrive speed Presence Pulse will short
Memory Functions Flow Chart (Figure
From Figure Part
DS1921H/Z
FUNCTIONS FLOW CHART Figure 13-2
Figure Part
From Figure Part
Skip ROM?
Overdrive Skip ROM?
Overdrive Match?
Master
Match? Master Master Reset Pulse? Match?
Master
From Figure Part
Match?
Figure Part
Always transmitted Overdrive speed.
DS1921H/Z
Overdrive Skip [3Ch]
single-drop this command save time allowing master access memory/control functions without providing 64-bit code. Unlike normal Skip command, Overdrive Skip sets DS1921H/Z Overdrive mode communication following this command occur Overdrive speed until reset pulse minimum 480µs duration resets devices standard speed When issued multidrop this command will Overdrive-supporting devices into Overdrive mode. subsequently address specific Overdrive-supporting device, reset pulse Overdrive speed issued followed Match Search command sequence. This will speed time search process. more than slave supporting Overdrive present Overdrive Skip command followed Read command, data collision will occur multiple slaves transmit simultaneously (open-drain pull-downs will produce wired-AND result).
Overdrive Match [69h]
Overdrive Match command followed 64-bit sequence transmitted Overdrive Speed allows master address specific DS1921H/Z multidrop simultaneously Overdrive mode. Only DS1921H/Z that exactly matches 64-bit sequence will respond subsequent memory/control function command. Slaves already Overdrive mode from previous Overdrive Skip successful Overdrive Match command will remain Overdrive mode. overdrive-capable slaves will return standard speed next Reset Pulse minimum 480µs duration. Overdrive Match command used with single multiple devices bus.
1-WIRE SIGNALING
DS1921H/Z requires strict protocols ensure data integrity. protocol consists four types signaling line: Reset Sequence with Reset Pulse Presence Pulse, Write Write Read Data. Except presence pulse master initiates these signals. DS1921H/Z communicate different speeds: standard speed Overdrive speed. explicitly into Overdrive mode, DS1921H/Z will communicate standard speed. While Overdrive mode fast timing applies waveforms. from idle active, voltage 1-Wire line needs fall from VPUP below threshold VTL. from active idle, voltage needs rise from VILMAX past threshold VTH. time takes voltage make this rise seen Figure duration depends pull-up resistor (RPUP) used capacitance 1-Wire network attached. voltage VILMAX relevant DS1921H/Z when determining logical level, triggering events. initialization sequence required begin communication with DS1921H/Z shown Figure Reset Pulse followed Presence Pulse indicates DS1921H/Z ready receive data, given correct memory function command. master uses slew-rate control falling edge, must pull down line tRSTL compensate edge. tRSTL duration 480µs longer will exit Overdrive mode returning device standard speed. DS1921H/Z Overdrive mode tRSTL longer than 80µs, device will remain Overdrive mode.
DS1921H/Z
INITIALIZATION PROCEDURE (RESET PRESENCE PULSES) Figure
MASTER RESET PULSE VPUP VIHMASTER VILMAX MASTER PRESENCE PULSE tMSP
tRSTL
tPDH MASTER
tPDL tRSTH
tREC DS1921H/Z
RESISTOR
After master released line goes into receive mode (RX). Now, 1-Wire pulled VPUP pull-up resistor case DS2480B driver, active circuitry. When threshold crossed, DS1921H/Z waits tPDH then transmits presence pulse pulling line tPDL. detect presence pulse, master must test logical state 1-Wire line tMSP. tRSTH window must least tPDHMAX, tPDLMAX, tRECMIN. Immediately after tRSTH expired, DS1921H/Z ready data communication. mixed population network, tRSTH should extended minimum 480µs standard speed 48µs Overdrive speed accommodate other 1Wire devices.
Read/Write Time Slots
Data communication with DS1921H/Z takes place time slots that carry single each. Write time slots transport data from master slave. Read time-slots transfer data from slave master. definitions write read time slots illustrated Figure communication begins with master pulling data line low. voltage 1-Wire line falls below threshold VTL, DS1921H/Z starts internal timing generator that determines when data line will sampled during write time slot long data will valid during read time slot.
Master Slave
write-one time slot, voltage data line must have crossed threshold after write-one time tW1LMAX expired. write-zero time slot, voltage data line must stay below threshold until write-zero time tW0LMIN expired. voltage data line should exceed VILMAX during entire tW0L tW1L window. After threshold been crossed, DS1921H/Z needs recovery time tREC before ready next time slot.
DS1921H/Z
READ/WRITE TIMING DIAGRAM Figure Write-One Time Slot
VIHMASTER VILMAX VPUP tW1L
RESISTOR
tSLOT MASTER
Write-Zero Time Slot
VIHMASTER VILMAX VPUP tW0L
RESISTOR
tSLOT MASTER
tREC
Read-Data Time Slot
VPUP VIHMASTER VILMAX RESISTOR tMSR Master Sampling Window tREC tSLOT MASTER DS1921H/Z
Slave Master
read-data time slot begins like write-one time slot. voltage data line must remain below until read time expired. During window, when responding with DS1921H/Z will start pulling data line low; internal timing generator determines when this pulldown ends voltage starts rising again. When responding with DS1921H/Z will hold data line all, voltage starts rising soon over. (rise rime) side internal timing generator DS1921H/Z other side define master sampling window (tMSRMIN tMSRMAX) which master must perform read from data line. most reliable communication, should short permissible master should read close later than tMSRMAX. After reading from data line, master must wait until tSLOT expired. This guarantees sufficient recovery time tREC DS1921H/Z ready next time slot.
DS1921H/Z
GENERATION
With DS1921H/Z there different types Cyclic Redundancy Checks (CRCs). 8-bit type stored most significant byte 64-bit ROM. master compute value from first bits 64-bit compare value stored within DS1921H/Z determine data been received error-free. equivalent polynomial function this This 8-bit received true (noninverted) form. computed factory lasered into ROM. other 16-bit type, generated according standardized CRC16-polynomial function This used error detection when reading data memory using Read Memory with command fast verification data transfer when writing reading from scratchpad. contrast 8-bit CRC, 16-bit always communicated inverted form. CRC-generator inside DS1921H/Z chip (Figure will calculate 16-bit shown command flow chart Figure master compares value read from device calculates from data decides whether continue with operation reread portion data with error. With initial pass through Read Memory with flow chart, 16-bit value result shifting command byte into cleared generator, followed address bytes data bytes. Subsequent passes through Read Memory with flow chart will generate 16-bit that result clearing generator then shifting data bytes. With Write Scratchpad command generated first clearing generator then shifting command code, target addresses data bytes. DS1921H/Z will transmit this only data bytes written scratchpad include scratchpad ending offset 11111b. data start location within scratchpad. With Read Scratchpad command generated first clearing generator then shifting command code, target addresses (TA1 TA2), byte, scratchpad data starting target address. DS1921H/Z will transmit this only reading continues through scratchpad, regardless actual ending offset. more information generating values Application Note Book DS19xx iButton Standards.
DS1921H/Z
CRC-16 HARDWARE DESCRIPTION POLYNOMIAL Figure
Polynomial
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
INPUT DATA
OUTPUT
Command-Specific 1-Wire Communication Protocol Legend
Symbol Select TA-E/S <data EOS> <data EOP> <data EOM> EOP> bytes> <data> CRC16\ loop loop loop Description 1-Wire Reset Pulse generated master 1-Wire Presence Pulse generated slave Command data satisfy function protocol (Skip ROM, Search ROM, etc.) Command "Write Scratchpad" Command "Read Scratchpad" Command "Copy Scratchpad" Command "Read Memory" Command "Read Memory with CRC" Command "Clear Memory" Command "Convert Temperature" Target Address TA1, Target Address TA1, with byte Transfer many data bytes needed reach scratchpad offset Transfer many data bytes needed reach memory page Transfer many data bytes needed reach datalog memory Transfer many bytes needed reach memory page boundary Transfer bytes Transfer undetermined amount data Transfer inverted CRC16 Indefinite loop where master reads bytes Indefinite loop where master reads bytes Indefinite loop where master reads bytes
DS1921H/Z
Command-Specific 1-Wire Communication Protocol Color Codes
Master slave Slave master
Write Scratchpad, reaching Scratchpad
Select <data EOS> CRC16\ loop
Write Scratchpad, reaching Scratchpad
Select <data>
Read Scratchpad
Select TA-E/S <data EOS> CRC16\ loop
Copy Scratchpad (success)
Select TA-E/S loop
Copy Scratchpad (invalid TA-E/S)
Select TA-E/S loop
Read Memory (success)
Select <data EOM> loop
Read Memory (invalid address)
Select loop
Reading reserved pages through through pages higher (beyond datalog memory) will result bytes.
Read Memory with (success)
Select <data EOP> CRC16\ bytes> Loop CRC16\
bytes" either valid page data bytes when reading reserved pages through through pages higher (beyond datalog memory).
DS1921H/Z
Read Memory with (invalid address)
Select EOP> CRC16\ bytes> Loop CRC16\
bytes" 00h.
Clear Memory
Select loop
verify success, read Status Register address 0214h. MEMCLR command executed successfully.
Convert Temperature
Select loop
read result verify success, read addresses 0211h (result) Device Samples Counter address 021Dh 021Fh. count incremented, command executed successfully.
DS1921H/Z
MISSION EXAMPLE: PREPARE START MISSION
Assumption: previous mission come end. ongoing mission write Status Register preparation DS1921H/Z mission including start mission requires four steps: Step needs adjusted) Step clear data previous mission Step search condition mission start delay, clear alarm flags Step temperature alarms write sample rate start mission
STEP
actual time 15:30:00 hours Monday, April 2002. This results following data written registers: Address: Data: 200h 201h 202h 203h 204h 205h 206h
With only single DS1921H/Z connected master, communication step follows:
MASTER MODE DATA (LSB FIRST) (Reset) (Presence) data bytes> (Reset) (Presence) data bytes> (Reset) (Presence) (Reset) (Presence) COMMENTS Reset pulse (480s 960µs) Presence pulse Issue Skip command Issue Write Scratchpad command TA1, beginning offset TA2, address 0200h Write bytes data scratchpad Reset pulse Presence pulse Issue Skip command Issue Read Scratchpad command Read TA1, beginning offset Read TA2, address 0200h Read E/S, ending offset flags Read scratchpad data verify Reset pulse Presence pulse Issue Skip command Issue Copy Scratchpad command (AUTHORIZATION CODE) Reset pulse Presence pulse
DS1921H/Z
STEP
EMCLR enable then execute Clear Memory command. oscillator must stable before Clear Memory command issued. Wait after issuing Clear Memory command before proceeding Step This results following data written Status Register: Address: Data: 20Eh
With only single DS1921H/Z connected master, communication step follows:
MASTER MODE DATA (LSB FIRST) (Reset) (Presence) (Reset) (Presence) (Reset) (Presence) (Reset) (Presence) (Reset) (Presence) COMMENTS Reset pulse (480s 960µs) Presence pulse Issue Skip command Issue Write Scratchpad command TA1, beginning offset TA2, address 020Eh Write status byte scratchpad Reset pulse Presence pulse Issue Skip command Issue Read Scratchpad command Read TA1, beginning offset Read TA2, address 020Eh Read E/S, ending offset 0Eh, flags Read scratchpad data verify Reset pulse Presence pulse Issue Skip command Issue Copy Scratchpad command (AUTHORIZATION CODE) Reset pulse Presence pulse Issue Skip command Issue Clear Memory command Reset pulse Presence pulse
DS1921H/Z
STEP
this example, rollover disabled search condition high temperature only. mission start with delay (005Ah) minutes alarm flags TLF, THF, cleared. This results following data written special function registers: Address: Data: 20Eh 20Fh 00h* 210h 00h* 211h 00h* 212h 213h 214h
Writing through address locations 20Fh 211h faster than accessing Mission Start Delay Register separate cycle. write attempt effect contents these registers. With only single DS1921H/Z connected master, communication step follows:
MASTER MODE DATA (LSB FIRST) (Reset) (Presence) data bytes> (Reset) (Presence) data bytes> (Reset) (Presence) (Reset) (Presence) COMMENTS Reset pulse (480s 960µs) Presence pulse Issue Skip command Issue Write Scratchpad command TA1, beginning offset TA2, address 020Eh Write bytes data scratchpad Reset pulse Presence pulse Issue Skip command Issue Read Scratchpad command Read TA1, beginning offset Read TA2, address 020Eh Read E/S, ending offset 14h, flags Read scratchpad data verify Reset pulse Presence pulse Issue Skip command Issue Copy Scratchpad command (AUTHORIZATION CODE) Reset pulse Presence pulse
DS1921H/Z
STEP
this example, temperature alarms temperature threshold high temperature threshold, assuming DS1921Z device. sample rate once every minutes, allowing mission last days. This results following data written special function registers: Address: Data: 20Bh 20Ch 20Dh
With only single DS1921H/Z connected master, communication step follows:
MASTER MODE DATA (LSB FIRST) (Reset) (Presence) data bytes> (Reset) (Presence) data bytes> (Reset) (Presence) (Reset) (Presence) COMMENTS Reset pulse (480s 960µs) Presence pulse Issue Skip command Issue Write Scratchpad command TA1, beginning offset TA2, address 020Bh Write bytes data scratchpad Reset pulse Presence pulse Issue Skip command Issue Read Scratchpad command Read TA1, beginning offset Read TA2, address 020Bh Read E/S, ending offset 0Dh, flags Read scratchpad data verify Reset pulse Presence pulse Issue Skip command Issue Copy Scratchpad command (AUTHORIZATION CODE) Reset pulse Presence pulse
step successful, Status Register will MEMCLR will mission start delay will counting down.
DS1921H/Z
PHYSICAL SPECIFICATION
Size Weight mechanical drawing 3.3g
ABSOLUTE MAXIMUM RATINGS*
Voltage Sink Current Temperature Range DS1921H, DS1921Z Storage Temperature Range -0.5V, 20mA -40°C +85°C** -40°C +50°C**
This stress rating only functional operation device these other conditions above those indicated operation sections this specification implied. Exposure absolute maximum rating conditions extended periods time affect reliability.
Storage operation above 50°C significantly reduces battery life.
ELECTRICAL CHARACTERISTICS
(VPUP 2.8V 5.25V, -40°C +85°C)
UNITS NOTES 1.14 0.71 1.00 0.66 2.70 2.70 0.30 2.70 2.70
PARAMETER SYMBOL CONDITIONS general data 1-Wire Pull-Up RPUP Resistance Input Capacitance Input Load Current VPUP High-to-Low VPUP 4.5V Switching Threshold Input Voltage Low-to-High VPUP 4.5V Switching Threshold Output voltage Recovery Time tREC Standard Speed, RPUP 2.2k Overdrive Speed, RPUP 2.2k Overdrive Speed, directly prior reset pulse; RPUP 2.2k Timeslot Duration tSLOT Standard Speed Overdrive Speed
DS1921H/Z
PARAMETER SYMBOL CONDITIONS pin, 1-Wire Reset, Presence Detect Cycle Reset Time tRSTL Standard Speed, VPUP 4.5V Standard Speed Overdrive Speed Presence Detect High tPDH Standard Speed Time Overdrive Speed Presence Detect tPDL Standard Speed Time Overdrive Speed Presence Detect tMSP Standard Speed Sample Time Overdrive Speed pin, 1-Wire Write Write-0 Time tW0L Standard Speed Overdrive Speed Write-1 Time tW1L Standard Speed Overdrive Speed pin, 1-Wire Read Read Time Standard Speed Overdrive Speed Read Sample Time tMSR Standard Speed Overdrive Speed Real-Time Clock Frequency Deviation -5°C +46°C Temperature Converter Tempcore Operating DS1921H Range DS1921Z Conversion Time tCONV Thermal Response RESP Time Constant Conversion Error Number NCONV Conversions
UNITS NOTES
(see graphs)
NOTES
System Requirement. Maximum allowable pull-up resistance function number 1-Wire devices system 1-Wire recovery times. specified value here applies systems with only device with minimum 1-Wire recovery times. more heavily loaded systems, active pull-up such that found DS2480B required. Capacitance could 800pF when power first applied. 2.2k resistor used pull data line, 2.5µs after VPUP been applied parasite capacitor will affect normal communication. Input load ground. voltages referenced ground. VTL, function internal supply voltage. Voltage below which, during falling edge logic detected. voltage needs less equal VILMAX whenever master drives line low.
DS1921H/Z
Voltage above which, during rising edge logic detected. characteristic linear voltages less than represents time required pull-up circuitry pull voltage from VTH. represents time required pull-up circuitry pull voltage from input high threshold master. This number derived from test conducted Cemagref Antony, France, July 2000. Test Report number temperature conversions Samples) possible with built-in energy source depends operating storage temperature device. When mission, oscillator should turned device should stored temperature exceeding +25°C. Under this condition shelf life time years minimum. Highlighted numbers compliance with published iButton standards. comparison table below. These values derived from simulation across process, voltage, temperature production tested. Total accuracy plus 1/16°C quantization 1/8°C digital resolution device. WARNING: sole method measuring tracking temperature and/or humidity products articles that could affect health safety persons, plants, animals, other living organisms, including limited foods, beverages, pharmaceuticals, medications, blood blood products, organs, flammable, combustible products. User shall assure that redundant other primary) methods testing determining handling methods, quality, fitness articles products should implemented. Temperature and/or humidity tracking with this product, where health safety aforementioned persons things could adversely affected, only recommended when supplemental redundant information sources used. Data logger products 100% tested calibrated time manufacture Dallas Semiconductor/Maxim ensure that they meet data sheet parameters, including temperature accuracy. User shall responsible proper storage this product. with sensor-based product, user shall also responsible occasionally rechecking temperature accuracy product ensure still operating properly. Standard Values Standard Speed Overdrive Speed 61µs (undef.) (undef.) 480µs (undef.) 48µs 80µs 15µs 60µs 60µs 240µs 24µs 60µs 120µs 16µs DS1921H/Z Values Standard Speed Overdrive Speed 65µs (undef.) (undef.) 540µs 640µs 48µs 80µs 15µs 60µs 1.1µs 60µs 270µs 7.5µs 24µs 60µs 120µs 15µs
Parameter Name tSLOT (incl. tREC) tRSTL tPDH tPDL tW0L
Intentional change, longer recovery time between time slots.
Frequency Deviation Temperature
DS1921H/Z
Lower Limit
Upper Limit
Frequency Deviation (PPM)
-100 -125 -150 -175 -200
Temperature (°C)
Minimum Product Lifetime Temperature Different Sample Rates
Every Minute Samples
11.00
Every Min. Osc.
Every Min.
Min. Product Lifetime (years)
10.00 9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00
Temperature (°C)
DS1921H/Z
Minimum Product Lifetime Sample Rate Different Temperatures
-5°C
12.00
26°C
37°C
46°C
Minimum Product Lifetime (years)
11.00 10.00 9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 1000
Minutes between Samples
DS1921H/Z
REVISION HISTORY
REVISION DATE DESCRIPTION Added bullet "Water resistant waterproof placed inside DS9107 iButton capsule (Exceeds Water Resistant Arequirements)". text Application section: Note that initial sealing level DS1921H/Z achieves IP56. Aging conditions degrade integrity seal over time, applications with significant exposure liquids, sprays, other similar environments, recommended place Thermochron DS9107 iButton capsule. DS9107 provides watertight enclosure that been rated IP68 (See www.maxim-ic.com/AN4126). Added sign PART numbers Ordering Information table, indicating RoHS-compliant packages. Removed UL#913 bullet from Common iButton Features section. PAGES CHANGED
120407
8/09
Maxim cannot assume responsibility circuitry other than circuitry entirely embodied Maxim product. circuit patent licenses implied. Maxim reserves right change circuitry specifications without notice time.
Maxim Integrated Products, Gabriel Drive, Sunnyvale, 94086 408-737-7600
2009 Maxim Integrated Products Maxim registered trademark Maxim Integrated Products, Inc.

DS1921H/Z High-Resolution Thermochron® iButton® Range +15°C +46°C

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