DS1904 iButton Real-Time Clock/calendar binary format Uses same b
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19-4864; 8/09
DS1904 iButton
Real-Time Clock/calendar binary format Uses same binary time/date representation DS1994 with second resolution Clock accuracy better than minutes month 25°C Operating temperature range from -40°C +70°C Over years operation
Presence detector acknowledges when reader first applies voltage Meets UL#913 (4th Edit.); Intrinsically Safe Apparatus, Approved under Entity Concept Class Division Group Locations (application pending)
MicroCan
5.89 0.51
COMMON iButton FEATURES
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 MicroLAN Digital identification information momentary contact Chip-based data carrier compactly stores information Data accessed while affixed object Economically communicates host with single digital signal 16.3k bits second Standard diameter 1-Wire® protocol ensure compatibility with iButton® Device family 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
16.25
000000FBC52B
1-Wire
17.35
dimensions shown millimeters
ORDERING INFORMATION
DS1904L-F5# MicroCan
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
iButton DESCRIPTION
DS1904 iButton rugged real-time clock module that accessed with minimal hardware. Data transferred serially 1-Wire protocol, which requires only single data lead ground return. DS1904 contains unique 64-bit factory-lasered real-time clock/calendar implemented binary counter. durable MicroCan package highly resistant environmental
1-Wire iButton registered trademarks Maxim Integrated Products, Inc.
DS1904
hazards such dirt, moisture, shock. Accessories permit DS1904 mounted almost surface including printed circuit boards plastic fobs. DS1904 adds functions such calendar, time date stamp, stopwatch, hour meter, interval timer, logbook type electronic device embedded application that uses microcontroller.
OVERVIEW
DS1904 main data components: 64-bit lasered ROM, real-time clock counter (Figure real-time clock utilizes on-chip oscillator that connected 32.768 crystal. hierarchical structure 1-Wire protocol shown Figure master must first provide four function commands: Read ROM, Match ROM, Search ROM, Skip ROM. protocol these functions described Figure After function command successfully executed, real-time clock functions become accessible master then provide real-time clock function commands. protocol these commands described Figure data read written least significant first.
BLOCK DIAGRAM Figure
CONTACT DATA FUNCTION CONTROL 64-BIT LASERED
CLOCK FUNCTION CONTROL READ/WRITE BUFFER LITHIUM COUNTER (32-BIT)
OSCILLATOR CONTROL
32.768 OSCILLATOR
DIVIDER
64-BIT LASERED
Each DS1904 contains unique code that bits long. first eight bits 1-Wire family code. next bits unique serial number. last eight bits first bits. (See Figure 1-Wire generated using polynomial generator consisting shift register gates shown Figure polynomial Additional information about Dallas Semiconductor 1-Wire Cyclic Redundancy Check available Book DS19xx iButton Standards. shift register bits initialized zero. Then starting with least significant family code, time shifted After family code been entered, then serial number entered. After 48th serial number been entered, shift register contains value. Shifting eight bits should return shift register zeros. 64-bit Function Control section allow DS1904 operate 1-Wire device follow 1-Wire protocol detailed section "1-Wire System".
DS1904
HIERARCHICAL STRUCTURE 1-WIRE PROTOCOL Figure
Master 1-Wire Other Devices
DS1904 Command Level Available Commands
Read Match Search Skip
Data Fields Affected
64-bit 64-bit 64-bit
1-Wire Function Commands (see Figure
DS1904 specific Function Commands (see Figure
Write Clock Read Clock
Counter, Device Control Counter, Device Control
64-BIT LASERED Figure
8-Bit Code 48-Bit Serial Number 8-Bit Family Code (24h)
1-WIRE GENERATOR Figure
Polynomial
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
STAGE
INPUT DATA
DS1904
TIMEKEEPING
32.768 crystal oscillator used time base real-time clock counter. oscillator turned under software control. oscillator must real time clock function. real-time clock counter double buffered. This allows master read time without data changing while being read. accomplish this, snapshot counter data transferred read/write buffer, which user accesses.
DEVICE CONTROL BYTE
on/off control 32.768 crystal oscillator done through device control byte. This byte read written through Clock Function commands. Device Control Byte
function
Bits hard-wired read 0's. Oscillator Enable/Disable
These bits control/report whether 32.768 crystal oscillator running. oscillator running, both bits will read oscillator turned these bits will read When writing device control byte both occurrences should have identical data. Otherwise value address (bold) takes precedence. General-purpose user flags
These non-volatile bits have particular function within chip. They read written under control application software.
REAL-TIME CLOCK
real-time clock 32-bit binary counter. incremented once second. real-time clock accumulate years seconds before rolling over. Time/date represented number seconds since reference point, which determined user. example, 12:00 a.m., January 1970 could reference point.
CLOCK FUNCTION COMMANDS
"Clock Function Flow Chart" (Figure describes protocols necessary accessing real-time clock. With only four bytes real-time clock control byte DS1904 does provide random access. Reading writing always starts with device control byte followed least significant byte time data.
DS1904
CLOCK FUNCTION COMMAND FLOW CHART Figure
Master Control Function Command Read Clock DS1904 copies Counter Buffer Write Clock Master Device Control Byte
Master Device Control Byte
Master Byte (7:0)
Master Byte (7:0)
Master next Byte (15:8)
Master next Byte (15:8)
Master next Byte (23:16) Master Byte (31:24)
Master next Byte (23:16) Master Byte (31:24)
Master Reset
Master Reset
Master Reset
DS1904 copies Buffer Counter
DS1904 Presence Pulse
DS1904
READ CLOCK [66h]
read clock command used read device control byte contents real-time clock counter. After having received most significant command code device copies actual contents real-time clock counter read/write buffer. master reads data beginning with device control byte followed least significant byte through most significant byte real-time clock. After this master continue reading from DS1904. data received will same first pass through command flow. read clock command ended point issuing Reset Pulse.
WRITE CLOCK [99h]
write clock command used real-time clock counter write device control byte. After issuing command, master writes first device control byte, which becomes immediately effective. After this master sends least significant byte through most significant byte written real-time clock counter. time data copied from read/write buffer real-time clock counter becomes effective master generates reset pulse. oscillator intentionally stopped, real-time clock counter behaves four-byte non-volatile memory.
1-WIRE SYSTEM
1-Wire system, which single master more slaves. instances DS1904 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 specified time slots that initiated falling edge sync pulses from master. more detailed protocol description, refer Chapter Book DS19xx iButton Standards.
HARDWARE CONFIGURATION Figure
MASTER Open Drain Port VPUP Typ. DS1904 1-WIRE PORT
DATA
RECEIVE TRANSMIT Typ.
MOSFET
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 3-state outputs. 1-Wire input DS1904 open drain with internal circuit equivalent that shown Figure multidrop consists 1-Wire with multiple slaves attached. 1Wire maximum data rate 16.3k bits second requires pull-up resistor approximately
DS1904
idle state 1-Wire high. reason transaction needs suspended, MUST left idle state transaction resume. this does occur left more than more devices reset. Since DS1904 gets energy operation through will perform power-on reset 1-Wire extended time period.
Transaction Sequence
protocol accessing DS1904 1-Wire port follows: Initialization Function Command Clock Function Command
INITIALIZATION
transactions 1-Wire begin with initialization sequence. initialization sequence consists reset pulse transmitted master followed presence pulse(s) transmitted slave(s). presence pulse lets master know that DS1904 ready operate. more details, "1-Wire Signaling" section.
FUNCTION COMMANDS
Once master detected presence, issue four function commands that DS1904 supports. function commands eight bits long. list these commands follows (refer flowchart Figure
Read [33h]
This command allows master read DS1904's 8-bit family code, unique 48-bit serial number, 8-bit CRC. This command should 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 48-bit serial number read master will invalid.
Match [55h]
match command, followed 64-bit sequence, allows master address specific DS1904 multidrop bus. Only DS1904 that exactly matches 64-bit sequence will respond following clock function command. slaves that match 64-bit sequence will wait reset pulse. This command used with single multiple devices bus.
SEARCH [F0h]
When system initially brought master might know number devices 1Wire their 64-bit codes. search command allows master process elimination identify 64-bit codes slave devices bus. search process repetition simple 3-step routine: read bit, read complement bit, then write desired value that bit. master performs this 3-step routine each ROM. After complete pass, master knows 64-bit code device. Additional passes will identify codes remaining devices. Chapter Book DS19xx iButton Standards comprehensive discussion search ROM, including actual example.
DS1904
FUNCTIONS FLOW CHART Figure
Master Reset Pulse DS1904 Presence Pulse Master Function Command Read Command Match Command Search Command Skip Command
DS1904 Family Code Byte
DS1904 Master DS1904 Master Match Match DS1904 Master DS1904 Master Match DS1904
DS1904 Serial Number Bytes
Match
DS1904 Byte
Master
DS1904 Master
Match
Match
Master Control Function Command (SEE FIGURE
DS1904
Skip [CCh]
This command save time single drop system allowing master access clock 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).
1-WIRE SIGNALING
DS1904 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. initialization sequence required begin communication with DS1904 shown Figure reset pulse followed presence pulse indicates DS1904 ready send receive data. master transmits (TX) reset pulse (tRSTL, minimum master then releases line goes into receive mode (RX). 1-Wire pulled high state pull-up resistor. After detecting rising edge data line, DS1904 waits (tPDH, 15-60 then transmits presence pulse (tPDL, 60-240
INITIALIZATION PROCEDURE "RESET PRESENCE PULSES" Figure
MASTER "RESET PULSE" VPULLUP tRSTL RESISTOR MASTER DS1904 tPDH tPDL VPULLUP MASTER "PRESENCE PULSE" tRSTH
tRSTL tRSTH tPDH tPDL
order mask interrupt signaling other devices 1-Wire tRSTL should always less than Includes recovery time
READ/WRITE TIME SLOTS
definitions write read time slots illustrated Figure master initiates time slots driving data line low. falling edge data line synchronizes DS1904 master triggering internal delay circuit. During write time slots, delay circuit determines when DS1904 will sample data line. read data time slot, transmitted, delay circuit determines long DS1904 will hold data line low. data "1", DS1904 will hold data line all.
DS1904
READ/WRITE TIMING DIAGRAM Figure
Write-one Time Slot
VPULLUP tLOW1
15µs 60µs RESISTOR MASTER tSLOT tLOW1 tREC DS1904 Sampling Window
VPULLUP
tSLOT
tREC
Write-zero Time Slot
VPULLUP 15µs 60µs LOW0 RESISTOR MASTER tLOW0 tSLOT tREC VPULLUP tSLOT tREC
DS1904 Sampling Window
Read-data Time Slot
VPULLUP tLOWR tRDV RESISTOR MASTER DS1904 tSLOT tLOWR tRELEASE tREC tRDV Master Sampling Window VPULLUP tSLOT tREC
tRELEASE
DS1904
PHYSICAL SPECIFICATION
Size Weight Expected Service Life Safety mechanical drawing grams years 25°C Meets UL#913 (4th Edit.); Intrinsically Safe Apparatus, Approval under Entity Concept Class Division Group Locations (application pending)
ABSOLUTE MAXIMUM RATINGS*
Voltage 1-Wire Ground Operating Temperature Storage Temperature -0.5V +7.0V -40°C +70°C -40°C +70°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.
ELECTRICAL CHARACTERISTICS
PARAMETER Logic Logic Output Logic Output Logic High Input Load Current SYMBOL
(VPUP=2.8V 6.0V; -40°C +70°C)
-0.3 VPUP UNITS NOTES
CAPACITANCE
PARAMETER Capacitance 1-Wire SYMBOL
25°C)
UNITS NOTES
ELECTRICAL CHARACTERISTICS
PARAMETER Time Slot Write Time Write Time Read Time Read Data Valid Release Time Read Data Setup Recovery Time Reset High Time Reset Time Presence Detect High Presence Detect Accuracy 25°C SYMBOL tSLOT tLOW1 tLOW0 tLOWR tRDV tRELEASE tREC tRSTH tRSTL tPDH tPDL
(VPUP=2.8V 6.0V; -40°C +70°C)
UNITS min/mth NOTES
exactly
DS1904
NOTES:
voltages referenced ground. VPUP external pull-up voltage. Input load ground. Read data setup time refers time host must pull 1-Wire read bit. Data guaranteed valid within this falling edge. Under certain voltage conditions VIL1MAX have reduced much 0.5V always guarantee presence pulse. reset time (tRSTL) should restricted maximum allow interrupt signaling, otherwise, could mask conceal interrupt pulses. master must read while data valid. Guaranteed design; production tested. This specification applies 1-Wire idle (high low). Communication 1-Wire adversely affect accuracy device. highest accuracy, connect DS1904 separate 1Wire port limit access minimum acceptable application.
DS1904
REVISION HISTORY
REVISION DATE 2/00 8/09 DESCRIPTION Initial release. Added Ordering Information reflect conversion RoHS-compliant product. PAGES CHANGED
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