AP082902.EXE available additional file Control Using C505L
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AP0829
AP082902.EXE available
additional file
Control Using C505L
This Application Note shows C505L used control Liquid Crystal Display. example provided uses C505L controller Converter implement simple voltmeter.
Author: Copeland S.M. Wong Microcontroller Applications
05.99, Rel.
Control Using C505L
Introduction.3 Theory Liquid Crystal Displays.3 Structure Liquid Crystal Displays Multiple Backplanes Reduce Count Control LCDs Controller C505L.11 Connecting C505L.12 Application.14 Hardware Connections Software Algorithms.15 Appendix Main.c.17 LCD.c Putchar.c LCD.h Reg505l.h
AP0829 ApNote Revision History Actual Revision Rel.02 Previous Revision: Rel.01 Page Page Subjects changed (since last release) actual Rel. prev. Rel. Real Time Clock Description, References Code Removed
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Introduction
many applications necessary microcontroller display some information user. Information displayed using Light Emitting Diodes (LEDs), segmented displays, matrix Liquid Crystal Displays (LCDs), segmented LCDs. Segmented LCDs popular because they less power than segmented displays, convey more information than individual LEDs, require fewer lines than matrix displays. This Application Note focuses interfacing Segmented LCDs Infineon C505L 8-bit microcontroller. example software demonstrates configuration controller Analog-to-Digital converter simple voltmeter. Theory Liquid Crystal Displays
Liquid Crystal Displays inexpensive, power means display information. Unfortunately, structure control schemes displays usually complicated. control becomes even more complicated when structure designed reduce display count. Structure Liquid Crystal Displays
Figure shows cross-section simple LCD. made liquid crystal sandwiched between thin, grooved filaments. Transparent electrodes placed above below this structure. placement electrodes defines segments display. "electrode, filament, liquid crystal" structure then sandwiched between layers glass. Polarizing filters then placed above piece glass below bottom piece glass. Beneath bottom filter usually reflector. Sometimes bottom polarizing filter reflector combined into single "polarizing reflector".
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Polarization Light
Polarizing Filter Glass Transparent Electrodes (segments) Grooved Filament Liquid Crystal (Twists Light) Grooved Filament Transparent Electrode (Backplane) Glass Polarizing Filter Reflective Surface
Figure Structure light enters filter, gets polarized. polarized light effected glass, transparent electrodes. liquid crystal molecules align themselves with grooves grooved filaments. grooves bottom filament rotated degrees with respect filament. This causes liquid crystal molecules twist like helix. polarized light passes through liquid crystal, remains polarized, twists degrees, shown Figure light then passes through bottom transparent electrode glass. bottom polarizing filter rotated degrees with respect filter. Since light that reaches bottom filter been twisted, passes through filter unaffected. light then reflected back through structure same way.
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Polarizing Filter Polarization Light
Grooved Filaments
Liquid Crystal Molecules
Polarizing Filter
Figure Liquid Crystal Twisting Polarized Light
there potential difference between electrode bottom electrode, molecules liquid crystal that between electrodes align themselves with electric field that generated. This means that liquid between electrodes will longer twist light that passes through this case, light will pass through filter polarized. will then unaffected glass, electrodes, liquid crystal. polarized light will pass through bottom filter because rotated degrees with respect filter shown Figure This causes area between plates appear dark. dark area referred segment. Since electrodes display physically touch each other, uses very little current. current that used capacitance electrodes.
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Control Using C505L
Polarizing Filter Transparent Electrode Polarization Light
Liquid Crystal Molecules
Transparent Electrode Light Pass Through Bottom Filter
Polarizing Filter
Figure Liquid Crystal with Externally Applied Potential Difference Multiple Backplanes Reduce Count
simple shown Figure bottom electrode covers entire surface LCD. This electrode referred backplane. segments defined shape electrodes Figure order individually control each segment, wire (and pin) must connected each electrode surface, additional will needed backplane. displays with large number segments, this solution practical. reduce number pins required drive display, often more than backplane used. When there more than backplane, more than electrode layer) connected same shown electrode configurations Figure When backplanes used each control segments. pins connected electrodes surface will referred column pins. backplane pins will referred pins. Having multiple (backplane) pins allows column pins form matrix, that each segment individually controlled selectively applying voltage appropriate column pin.
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Backplanes (Rows) Single Backplane
Figure Electrode Configuration Single Multiple Backplane LCDs Unfortunately, when multiple backplanes, impossible control segments using static voltages. example, consider multiple backplane Figure Let's assume that wishes activate segments column column this, static voltages applied pins. Suppose addition these segments, wishes activate segment column only this apply static voltage this will also cause segment column become active. control combination segments column signals must time multiplexed (there other reasons static voltages cannot used LCDs). controller C505L ability control backplanes columns. This means that segments controlled.
Control LCDs
Unfortunately, voltage difference between electrodes maintained long, liquid crystal become permanently aligned direction, thus ruining display. ensure that liquid does become permanently aligned, voltage difference between plates must toggled between positive negative. Since
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Control Using C505L
voltages that applied crystal must toggled periodically, control scheme becomes even more complicated. When controller C505L activated, applies voltages shown Figure (backplane) pins. These signals periodic generated controller with intervention.
Frame
1/fLCD
Time
Time
Time
Time
Figure Voltage Applied Pins voltage levels, created C505L's board programmable converter. programmable using on-chip converter, voltages always (2÷3)U3, respectively. Since converter programmable, C505L used wide variety LCDs. value also changed fly" adjust contrast display.
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Control Using C505L
timing signals Figure also programmable. controller dedicated timer unit which used provide clock signal controller. clock frequency (fLCD) programmable controller also clocked on-board Real Time Clock unit (this allows remain active even during power-down mode). Since signals vary according Figure constant voltage column pins would cause segments become active. stop segments from becoming active, voltage shown Figure (solid line) applied each column signal.
Cx/R0 Frame Cx/R1
1/fLCD
Voltage Column Voltage
Time
Cx/R2 Cx/R3
Time
Time
Time
Figure Column Voltage Segments remain inactive Figure shows column signal that should applied ensure that segment activated. dotted lines Figure represent signals from Figure
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Control Using C505L
Figure indicates, voltage difference between column pins never more than which enough activate segment. Like signals, column signals generated without intervention. activate segment, column voltages should varied that larger voltage applied. Figure voltages varied that segments will activated segments will remain inactive.
Cx/R0
Frame
1/fLCD
Voltage Column Voltage
Active Cx/R1 Time Active Time
Cx/R2 Active
Cx/R3 Active
Time
Time
Figure Activation Segments Figure indicates, column connected four segments, segments would activated segments would remain inactive.
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Control Using C505L
segment active when voltage difference present pins. Figure shows, voltage difference alternates between active segments. This keeps liquid crystal molecules from becoming permanently aligned direction. indicated Figure activated segments only receive full voltage difference during eight 1/fLCD periods that make frame. Since segments only active frame, this control scheme referred driving method. Since each column controls segments, power different voltage sequences required each column pins order fully control segments LCD. controller C505L ability this without intervention. Controller C505L
controller C505L makes possible ignore details structure control presented previous sections. Figure shows block diagram controller C505L.
15-bit Reload Reg.: CSEL fosc fRTC 15-bit Down Counter Underflow
LCEN Current Scaling Network Converter 8-bit (V3): DAC0 8-bit Segment Regs.: DIGn fLCD Segment Controller Lines
Column Lines
Figure Block Diagram Controller
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Control Using C505L
C505L allows great deal flexibility choosing LCD. maximum voltage applied controlled DAC0 register. frequency LCD) controlled 15-bit reload value placed LCRH LCRL registers. 15-bit down counter clocked external system oscillator, Real Time Clock oscillator. C505L generates outputs column outputs. fewer than column outputs needed, pins used digital pins. There 8-bit registers that used individually control segments. Each these registers represents segment. Setting activates segment automatically applying appropriate voltages timing column pins. Setting multiple bits activates multiple segments. Each registers controls consecutive column outputs shown Figure
DIGm (0xF3Em) C(n+1),R3 Cn,R3 C(n+1),R2 Cn,R2 C(n+1),R1 Cn,R1 Cn,R0 C(n+1),R0
Figure Segment Registers Connecting C505L
When connecting C505L, important consider order which column pins connected LCD. example, consider that made identical characters each with segments. Each character controlled column pins shown Figure
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C505L
Figure Connection type display shown Figure would more convenient (but necessary) connected such that first character display controlled pins, second character controlled pins, etc. When display connected this manner, each DIGm register controls character LCD. writing 0x15 DIG0 makes appear first character display, writing 0x15 DIG1 will make appear second character display. This type consistency makes working with much easier. evaluation board C505L Starter uses that eight characters. Each character contains segments. constructed such that each character controlled column pins. schematic evaluation board shows, each character controlled completely consecutive registers. This convenient when programming because registers that control each character defined single variable since they located consecutive memory addresses. Figure shows first character Starter evaluation board connected C505L. other seven characters display connected similar manner.
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Control Using C505L
C505L DIG1 DIG0
Figure Connection Evaluation Board should noted that connecting shown Figure Figure necessary, make displaying text easier. Displays that contain symbols other non-text information, displays that have small number text characters connected that suites circuit designer programmer.
Application
demonstrate configuration C505L controller, example program been created. example application uses controller converter implement simple volt meter. Hardware Connections
application designed easily with C505L Starter Kit. C505L starter Electronics VIM-878 segment character display. Figure shows each character display configured. configuration shown Figure makes easy control each character associating character with integer variable. bits each variable control segments each character.
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Control Using C505L
Segment
Column
DIGn (0xF3En)
DIGn+1 (0xF3En+1)
Figure Configuration Evaluation Board
This application requires onboard analog-to-digital converter C505L. converter external reference voltage ground (VAREF VAGND) must applied. this example VAREF should connected VAGND should connected These connections already made starter board. This example will channel (P1.4) read externally applied analog voltage.
Software Algorithms
example software this application note implements voltmeter. voltmeter implemented very simply using converter controller C505L. Timer interrupt used initiate conversion ensure even distribution sampling points. Figure shows structure software.
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Main Program Initialize Peripherals Start Timer Endless "While" Loop Timer Start Conversion
Average Samples Convert Volts Display
Figure Structure Voltmeter Software Below brief description peripherals configured: Timer Timer placed Mode timer with divide prescaler). This causes interrupt occur every (8192)* fosc seconds (4.096 with external clock). Timer Interrupt Service Routine (ISR), conversion started. Converter converter placed single conversion mode (bit When conversion complete, interrupt generated. reads bits result. This provides accuracy approximately digits right decimal displayed LCD. results averaged together. Averaging results ensures consistent result still allows results contained integer variable. average samples then converted into volts multiplying 91/93. This provides closest approximation that accomplished using simple integer math (the exact conversion 5*100/511). resulting value then displayed decimal format decimal point added after second digit. Appendix shows code application. code created with Keil compiler.
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Appendix
Main.c
#include <Reg505L.h> C505L SRFs #include <LCD.h> Configuration #include <stdio.h> Contains printf Application Example ApNote 8029 "LCD Control Using C505L"
Main Routine void main(void) /////////////// Functions //////////////// void Init(void);
Init(); while (1);
Initialize LCD, A/D, Enable Interrupts Start Timer endless loop
Initialization Function Initializes controller, Timer Converter void Init(void) //// Initialize Controller ///////////////////// SYSCON 0x20; ENABLE ACCESS LCD/RTC/XRAM LCON 0xC1; ENABLE OUTPUTS ENABLE CONTROLLER SYSTEM CLOCK TIMER DAC0 LCD_Volt; VALUE LCRL 0x1B; VALUES fLCD LCRH 0xC1; START TIMER //// Initialize Timer ////////////////////////////// TMOD 0x00; mode Enable overflow interrupt //// Initialize Converter ////////////////////// SYSCON 0x10; ENABLE ACCESS P1ANA
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EAN4 SYSCON ADCON0 ADCON1 0xEF; 0x00; 0x44; EANBLE CHANNEL DISABLE ACCESS P1ANA SINGLE CONVERSION fADC fOSC/8 SELECT CHANNEL (P1.4) ENABLE INTERRUPT
EADC 0x02; 0x01;
Interrupt Priority Levels higher priority than
Timer Overflow this conversion started void T0ISR (void) interrupt ADDATL 0x01; conversion started writing dummy value ADDATL
Conversion Complete this ISR, converter readings averaged. converter results converted Volts. Volt value converted into digits display LCD. void ADC_ISR (void) interrupt /////////// Variables /////////////// static unsigned count Counter Averaging reads static unsigned unsigned avg; unsigned volt; unsigned temp; count ((((int)ADDATH) (ADDATL 7)); (count 128) temp volt temp only digits
Stop timer Calculate average voltage convert volts*100
printf("\n%03u %s", volt, "VOLT"); DIG[0] DIG[0] decimal_point;
Decimal Point
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0x0000; count 0x00; IADC reset next average start timer Clear converter interrupt request flag
LCD.c
THIS FILE CONVERTS REGISTERS C505L INTO SINGLE ARRAY TYPE DigType (DEFINED LCD.H). #include <LCD.h> xdata DigType DIG[DispLen _at_ 0xF3E0; Define registers array
Putchar.c
This file part Compiler package Copyright 1995-1996 Keil Software, Inc. PUTCHAR.C: This routine general character output C51. translate this file with following invocation: PUTCHAR.C <memory model> link modified PUTCHAR.OBJ file your application following BL51 invocation: BL51 <your object file list>, PUTCHAR.OBJ <controls> THIS FILE BEEN MODIFIED MIKE COPELAND INFINEON. THIS FILE DIRECTS OUTPUTS CONTROLLER C505L. FILES "LCD.H" "LCD.C" NEEDED. SINCE DISPLAY ONLY LINE "/n" WILL CLEAR DISPLAY. "printf" FUNCTION KEIL COMPILER USES THIS FUNCTION. 7/98
#include <LCD.h> char putchar (char
DigType code ASCII_TABLE[128] {let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_X,
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Control Using C505L
space, let_X, let_X, let_X, dollar_sign, let_X, let_X, apostrophe, let_X, let_X, asterisk, plus_sign, let_X, minus_sign, decimal_point, forward_slash, num_0, num_1, num_2, num_3, num_4, num_5, num_6, num_7, num_8, num_9, let_X, let_X, let_X, let_X, let_X, let_X, let_X, let_A, let_B, let_C, let_D, let_E, let_F, let_G, let_H, let_I, let_J, let_K, let_L, let_M, let_N, let_O, let_P, let_Q, let_R, let_S, let_T, let_U, let_V, let_W, let_X, let_Y, let_Z, let_X, back_slash, let_X, let_X, underscore, let_X, let_A, let_B, let_C, let_D, let_E, let_F, let_G, let_H, let_I, let_J, let_K, let_L, let_M, let_N, let_O, let_P, let_Q, let_R, let_S, let_T, let_U, let_V, let_W, let_X, let_Y, let_Z, let_X, or_sign, let_X, let_X, let_X}; unsigned char unsigned long static unsigned char place;
'\n') DispLen; i++) clear display DIG[i] space; instead place else (place DispLen) j<0x00010000; j++); delay scrolling place DispLen i<DispLen-1; i++) scroll DIG[i] DIG[i+1]; DIG[place] ASCII_TABLE[c]; place return
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LCD.h
This header file defines commonly used characters used KitCON 505L Change this header file different #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define #define let_A 0x341E Letters let_B 0x741E let_C 0x5402 let_D 0x1421 let_F 0x340A let_G 0x741A let_H 0x341C let_J 0x5014 let_K 0x9C08 let_P 0x340E let_Q 0xD416 let_R 0xB40E let_U 0x5414 let_W 0x9434 let_X 0x8821 let_Y 0x0881 let_Z 0x4822 let_S 0x641A let_I 0x4182 let_E 0x740A let_M 0x1C15 let_N 0x9415 let_V 0x1C20 let_O 0x5416 let_L 0x5400 let_T 0x0182 num_1 0x0014 Numbers num_2 0x700E num_3 0x601E num_4 0x241C num_5 0x641A num_6 0x741A num_7 0x0016 num_8 0x741E num_9 0x641E num_0 0x5C36 decimal_point 0x0040 apostrophe 0x0200 space 0x0000 dollar_sign 0x659A asterisk 0xA9A9 plus_sign 0x2188 minus_sign 0x2008 forward_slash 0x0820 back_slash 0x8001 underscore 0x4000 or_sign 0x0180 smile 0x5811
Decimal Point Apostrophe Segments active
Smiley face
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#define DispLen0x08 #define LCD_Volt 0xA0 Number digits Voltage applied
typedef unsigned DigType; Some displays will char type instead type extern xdata DigType DIG[DispLen Define registers array
Reg505l.h
SYMBOL Definition File C505L Author R.Schmid, Rev./ Date 17.10.97 Revision History V1.0 Original version //DEV C505L Special Function Registers 0x80; 0x81; 0x82; 0x83; WDTREL 0x86; PCON 0x87; TCON 0x88; #define PCON1 TCON TMOD 0x89; 0x8A; 0x8B; 0x8C; 0x8D; 0x90; #define P1ANA XPAGE =0x91; DPSEL =0x92; SCON 0x98; SBUF 0x99; 0xA0; IEN0 0xA8; 0xA9; SRELL =0xAA; 0xB0; SYSCON 0xB1; IEN1 0xB8; 0xB9; SRELH =0xBA; IRCON =0xC0; CCEN 0xC1; CCL1 0xC2; CCH1 0xC3; CCL2 0xC4;
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Control Using C505L
//SFR sbit sbit sbit sbit sbit sbit sbit sbit #define //SFR sbit sbit sbit sbit sbit //SFR sbit sbit sbit sbit sbit sbit sbit sbit //SFR sbit sbit sbit sbit sbit sbit sbit CCH2 0xC5; T2CON =0xC8; CRCL 0xCA; CRCH 0xCB; 0xCC; 0xCD; 0xD0; ADCON0 0xD8; ADDATH 0xD9; ADDATL 0xDA; ADCON1 0xDC; 0xE0; 0xE8; 0xF0; 0xF8; 0xFC; 0xFD; 0xFE; Bitaddressable Special Function Register Bits TCON EPWD PCON1 TCON^0; TCON^1; TCON^2; TCON^3; TCON^4; TCON^5; TCON^6; TCON^7;
INT4 =P1^1; INT5 =P1^2; T2EX =P1^5; CLKOUT P1^6; P1^7; P1ANA EAN0 =P1ANA^0; EAN1 =P1ANA^1; EAN2 =P1ANA^2; EAN3 =P1ANA^3; EAN4 =P1ANA^4; EAN5 =P1ANA^5; EAN6 =P1ANA^6; EAN7 =P1ANA^7; SCON
SCON^0; SCON^1; SCON^2; SCON^3; SCON^4; SCON^5; SCON^6;
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sbit //SFR sbit sbit sbit sbit sbit sbit sbit sbit //SFR sbit sbit sbit sbit sbit sbit sbit sbit //SFR sbit sbit sbit sbit sbit sbit sbit //SFR sbit sbit sbit sbit sbit sbit sbit //SFR sbit sbit sbit sbit sbit sbit sbit //SFR sbit sbit sbit sbit sbit sbit sbit SCON^7; IEN0
IEN0^0; IEN0^1; IEN0^2; IEN0^3; IEN0^4; IEN0^5; IEN0^6; IEN0^7;
P3^0; P3^1; INT0 =P3^2; INT1 =P3^3; P3^4; P3^5; P3^6; P3^7; IEN1 EADC =IEN1^0; IEN1^2; IEN1^3; IEN1^4; IEN1^5; SWDT =IEN1^6; EXEN2 IEN1^7; IRCON IADC =IRCON^0; IEX3 =IRCON^2; IEX4 =IRCON^3; IEX5 =IRCON^4; IEX6 =IRCON^5; IRCON^6; EXF2 =IRCON^7; T2CON T2I0 =T2CON^0; T2I1 =T2CON^1; T2CM =T2CON^2; T2R0 =T2CON^3; T2R1 =T2CON^4; I3FR =T2CON^6; T2PS =T2CON^7;
PSW^0; PSW^1; PSW^2; PSW^3; PSW^4; PSW^5; PSW^6;
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sbit //SFR sbit sbit sbit sbit sbit sbit sbit #define #define #define #define ADCON PSW^7;
ADCON0^0; ADCON0^1; ADCON0^2; ADCON0^3; ADCON0^4; ADCON0^6; ADCON0^7;
Special Function Register Module LCON(* ((unsigned char volatile xdata 0xF3DD)) LCRL ((unsigned char volatile xdata 0xF3DE)) LCRH ((unsigned char volatile xdata 0xF3DF)) DAC0 ((unsigned char volatile xdata 0xF3DC))
These registers defined global array (LCD.c) #define DIG0 ((unsigned char volatile xdata 0xF3E0)) #define DIG1 ((unsigned char volatile xdata 0xF3E1)) #define DIG2 ((unsigned char volatile xdata 0xF3E2)) #define DIG3 ((unsigned char volatile xdata 0xF3E3)) #define DIG4 ((unsigned char volatile xdata 0xF3E4)) #define DIG5 ((unsigned char volatile xdata 0xF3E5)) #define DIG6 ((unsigned char volatile xdata 0xF3E6)) #define DIG7 ((unsigned char volatile xdata 0xF3E7)) #define DIG8 ((unsigned char volatile xdata 0xF3E8)) #define DIG9 ((unsigned char volatile xdata 0xF3E9)) #define DIG10 ((unsigned char volatile xdata 0xF3EA)) #define DIG11 ((unsigned char volatile xdata 0xF3EB)) #define DIG12 ((unsigned char volatile xdata 0xF3EC)) #define DIG13 ((unsigned char volatile xdata 0xF3ED)) #define DIG14 ((unsigned char volatile xdata 0xF3EE)) #define DIG15 ((unsigned char volatile xdata 0xF3EF)) Special Function Registers #define RTCON ((unsigned char volatile xdata 0xF3F0)) #define RTCR0 ((unsigned char volatile xdata 0xF3F1)) #define RTCR1 ((unsigned char volatile xdata 0xF3F2)) #define RTCR2 ((unsigned char volatile xdata 0xF3F3)) #define RTCR3 ((unsigned char volatile xdata 0xF3F4)) #define RTCR4 ((unsigned char volatile xdata 0xF3F5)) #define CLREG0 ((unsigned char volatile xdata 0xF3F6)) #define CLREG1 ((unsigned char volatile xdata 0xF3F7)) #define CLREG2 ((unsigned char volatile xdata 0xF3F8)) #define CLREG3 ((unsigned char volatile xdata 0xF3F9)) #define CLREG4 ((unsigned char volatile xdata 0xF3FA)) #define RTINT0 ((unsigned char volatile xdata 0xF3FB)) #define RTINT1 ((unsigned char volatile xdata 0xF3FC)) #define RTINT2 ((unsigned char volatile xdata 0xF3FD)) #define RTINT3 ((unsigned char volatile xdata 0xF3FE)) #define RTINT4 ((unsigned char volatile xdata 0xF3FF))
AP0829 05.99
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