;*************************************************************************** ; ; AT Keyboard Interface V1.04 ; =========================== ; ; written by Peter Luethi, 12.07.2000, Switzerland ; http://www.electronic-engineering.ch ; last update: 19.04.2004 ; ; V1.04: Re-structured ISR to comply with latest modules, added ; label _ISR_RS232error ; (19.04.2004) ; ; V1.03: Improved AT keyboard and RS232 initialization, ; fixed RBIF/INTF interrupt initialization issue. ; Changed keyboard data pin to PORTA,4 (open-collector). ; (16.08.2003) ; ; V1.02: Made forward compatible (yes, this is feasible) by ; implementing/completing ALT and CTRL flags. Added ; labels to support non-implemented ALT and CTRL ; enhancements. (3.1.2002) ; ; V1.01: Changed from non-preemptive to preemptive interrupt-based ; keyboard scan pattern acquisition scheme. ; Now only the scan pattern acquisition is carried out ; during the interrupt service routine, the decoding ; happens during normal operation mode when the flag ; "KBDflag" has been set after having completed the entire ; scan pattern reception. (16.7.2001) ; ; V1.00: Initial release (12.7.2000) ; ; This code and accompanying files may be distributed freely and ; modified, provided this header with my name and this notice remain ; intact. Ownership rights remain with me. ; You may not sell this software without my approval. ; ; This software comes with no guarantee or warranty except for my ; good intentions. By using this code you agree to indemnify me from ; any liability that might arise from its use. ; ; ; SPECIFICATIONS: ; =============== ; Processor: Microchip PIC 16F84 ; Clock Frequency: 4.00 MHz XT ; Throughput: 1 MIPS ; RS232 Baud Rate: 9600 baud (depends on the module included) ; Serial Output: 9600 baud, 8 bit, no parity, 1 stopbit ; Keyboard Routine Features: Capability of uni-directional ; communication between microcontroller ; and keyboard ; Acquisition Methodology: Preemptive, interrupt-based ; keyboard scan pattern acquisition ; routine, with decoding to ASCII ; characters during normal operation ; Code Size of entire Program: 523 instruction words ; Required Hardware: AT Keyboard, MAX 232 ; Required Software: RS232 terminal ; ; ; ABSTRACT: ; ========= ; This routine converts AT keyboard scan patterns to ASCII characters ; and transmits them afterwards to the target device by using the ; RS232 transmission protocol. ; Support of english (QWERTY) and modified swiss-german (QWERTZ) ; 'codepages'. This implementation features no visual interface. ; Unidirectional data flow: Transmission only for characters typed on ; the local keyboard. ; ; ; DESCRIPTION: ; ============ ; Developed and tested on PIC 16F84. ; Any key stroke on the keyboard connected to the PIC will send the ; corresponding scan code from the keyboard to the microcontroller. ; Afterwards, the microcontroller converts the keyboard scan code to ; ASCII characters and sends them to the computer terminal via the ; RS232 connection. ; ; The keyboard scan pattern capture and decoding is done by an ; interrupt service routine. The event, which triggers the interrupt ; is a falling edge on the keyboard clock line at the KBDclkpin ; (PORTB,0). The keyboard data (scan code) will be fetched at the ; KBDdatapin (PORTA,4). ; There is only RS232 transmission, so only the TXport (PORTA,0) is ; connected. Since PORTB,0 is already used by the keyboard clock line, ; there exists no possibility to use it also for RS232 reception. ; The configuration of the KBDclkpin interrupt is done by the ; KEYBOARDinit macro. ; ; For the AT keyboard layout, English and modified Swiss-German ; 'codepages' are supported: ; QWERTY and QWERTZ keyboard layout ; ; ; IMPLEMENTED FEATURES: ; ===================== ; - Uni-directional communication between microcontroller application ; and remote RS232 client. ; - Uni-directional communication between microcontroller and keyboard. ; - Support for all keyboard characters typed with shift button active ; and inactive. ; - English and modified Swiss-German 'codepages' available ; (QWERTY and QWERTZ) ; Include the desired keyboard lookup tables at the correct location. ; - Caps Lock implemented ; - Num Lock always active ; - Possibility to implement short-cuts or user defined characters ; for 'Esc', 'Num Lock', 'Scroll Lock' and 'F1' - 'F12' keys ; ; - Further enhancement, not implemented: Support of ASCII conversion ; from direct ALT-DEC and CTRL-HEX entries, e.g. ALT + 6 + 4 = @ ; or CTRL + 3 + F = ? ; ; ; LIMITATIONS: ; ============ ; - No support for ALT-GR characters. ; - Minimized keyboard routine with support for only uni-directional ; communication from keyboard to controller, therefore no control ; over keyboard status LEDs. ; - No support for arrow buttons, 'Home', 'Del', 'PageUp', 'PageDown', ; 'Insert', 'End' because there exists no character/command ; corresponding to the ASCII character map. (But it is possible to ; use them for short-cuts or user defined characters, if the special ; code routine (0xE0) is altered.) ; ; ; NOTE: ; ===== ; This program needs 'ORG' directives to locate tables within entire ; memory pages. To allow for slight modifications, the code has not ; been optimized to the utmost extent regarding program memory ; placement. This can be carried out using the program memory window ; of MPLAB showing the hexadecimal representation of the code. ; ; ; CREDITS: ; ======== ; - Craig Peacock, the author of the excellent page about keyboards ; "Interfacing the PC's Keyboard" available at his website: ; http://www.beyondlogic.org/keyboard/keybrd.htm ; - Steve Lawther for inspirations concerning the scan code fetch ; routine (for bring-up version 1.00 of this program). ; ;*************************************************************************** ;***** COMPILATION MESSAGES & WARNINGS ***** ERRORLEVEL -207 ; Found label after column 1. ERRORLEVEL -302 ; Register in operand not in bank 0. ;***** PROCESSOR DECLARATION & CONFIGURATION ***** PROCESSOR 16F84 #include "p16f84.inc" ; embed Configuration Data within .asm File. __CONFIG _CP_OFF & _WDT_OFF & _PWRTE_ON & _XT_OSC ;***** MEMORY STRUCTURE ***** ;ORG 0x00 processor reset vector, declared below ;ORG 0x04 interrupt service routine, declared below ;***** PORT DECLARATION ***** #define TXport PORTA,0x00 ; RS232 output port, could be #define TXtris TRISA,0x00 ; any active push/pull port #define KBDdatapin PORTA,0x04 ; keyboard data input port #define KBDdatatris TRISA,0x04 ; (open-collector pin) #define KBDclkpin PORTB,0x00 ; keyboard clock input port (IntB) #define KBDclktris TRISB,0x00 ; @ INTF interrupt source (RB0) ;***** CONSTANT DECLARATION ***** CONSTANT BASE = 0x0C ; Base address of user file registers ;***** REGISTER DECLARATION ***** TEMP1 set BASE+d'0' ; Universal temporary register TEMP2 set BASE+d'1' ; ATTENTION !!! TEMP3 set BASE+d'2' ; They are used by various modules. TEMP4 set BASE+d'3' ; If you use them, make sure not to use ; them concurrently ! FLAGreg equ BASE+d'4' ; register containing keyboard and other flags TXD equ BASE+d'5' ; RS232 TX-Data register RXD equ BASE+d'6' ; RS232 RX-Data register (not used here, but m_rs232 ; requires its declaration) KBDcnt equ BASE+d'7' ; IRQ based keyboard scan pattern counter KBD equ BASE+d'8' ; keyboard scan code & ascii data register KBDcopy equ BASE+d'9' ; keyboard scan code register #define RELflag FLAGreg,0x00 ; release flag (0xF0) #define SHIflag FLAGreg,0x01 ; shift flag (0x12 / 0x59) #define SPEflag FLAGreg,0x02 ; special code flag (0xE0) #define CAPflag FLAGreg,0x03 ; caps lock flag (0x0D) #define ALTflag FLAGreg,0x04 ; ALT flag (0x11) #define CTRLflag FLAGreg,0x05 ; CTRL flag (0x14) #define KBDflag FLAGreg,0x06 ; keyboard data reception flag ; interrupt context save/restore W_TEMP equ BASE+d'10' ; context register (ISR) STATUS_TEMP equ BASE+d'11' ; context register (ISR) PCLATH_TEMP equ BASE+d'12' ; context register (ISR) FSR_TEMP equ BASE+d'13' ; context register (ISR) ;***** INCLUDE FILES ***** ORG 0x190 #include "..\..\m_bank.asm" #include "..\..\m_wait.asm" #include "..\..\m_rs096.asm" ; 9600 baud @ 4 MHz ;***** MACROS ***** KEYBOARDinit macro BANK1 bsf KBDclktris ; set keyboard clock line to input explicitely bsf KBDdatatris ; set keyboard data line to input explicitely bcf OPTION_REG,INTEDG ; keyboard interrupt on falling edge BANK0 bsf INTCON,INTE ; enable RB0/INT interrupts endm ;***** INTERRUPT SERVICE ROUTINE ***** ORG 0x04 ; interrupt vector location ISR ;************************ ;*** ISR CONTEXT SAVE *** ;************************ bcf INTCON,GIE ; disable all interrupts btfsc INTCON,GIE ; assure interrupts are disabled goto ISR movwf W_TEMP ; context save: W swapf STATUS,W ; context save: STATUS movwf STATUS_TEMP ; context save clrf STATUS ; bank 0, regardless of current bank movfw PCLATH ; context save: PCLATH movwf PCLATH_TEMP ; context save clrf PCLATH ; page zero, regardless of current page bcf STATUS,IRP ; return to bank 0 movfw FSR ; context save: FSR movwf FSR_TEMP ; context save ;*** context save done *** ;************************** ;*** ISR MAIN EXECUTION *** ;************************** ;***************************************** ;*** KEYBOARD SCAN PATTERN ACQUISITION *** ;***************************************** ;*** check start bit *** tstf KBDcnt ; check bnz _KBDdat ; branch on no zero btfsc KBDdatapin ; test start bit of keyboard data input goto _KBDabort ; no valid start bit, abort goto _INCF ; exit ;*** keyboard scan pattern acquisition *** _KBDdat movfw KBDcnt ; get kbd scan pattern acquisition counter sublw d'8' ; w = d'8' - KBDcnt (*) bnc _KBDpari ; branch if negative (carry == 0) btfss KBDdatapin ; get keyboard data input bcf KBD,0x07 ; (bit operations do not alter zero flag) btfsc KBDdatapin bsf KBD,0x07 bz _INCF ; exit on zero (zero flag still valid from (*)) rrf KBD,F ; do this only 7 times goto _INCF ; exit ;*** ignore parity bit *** _KBDpari movfw KBDcnt ; get kbd scan pattern acquisition counter sublw d'9' ; w = d'9' - KBDcnt bnc _KBDstp ; branch if negative (carry == 0) goto _INCF ; exit ;*** check stop bit *** _KBDstp btfss KBDdatapin ; check if stop bit is valid goto _KBDabort ; if not set, abort bsf KBDflag ; else set reception flag to decode KBD ;*** stall keyboard *** ; to prevent the arrival of more data before having finished decoding BANK1 ; hold keyboard (with kbd clk low): bcf KBDclktris ; set clk line to output BANK0 bcf KBDclkpin ; set keyboard clk line low (stall) ;*** disable RB0/INT interrupt line *** bcf INTCON,INTE ; disable RB0/INT interrupt goto _KBDterm ; terminate successfully _KBDabort clrf KBD ; abort / invalid data _KBDterm clrf KBDcnt ; reset kbd scan pattern acquisition counter goto _KBDend ; terminate execution of keyboard ISR ;*********************************** ;*** CLEARING OF INTERRUPT FLAGS *** ;*********************************** ; NOTE: Below, I only clear the interrupt flags! This does not ; necessarily mean, that the interrupts are already re-enabled. ; Basically, interrupt re-enabling is carried out at the end of ; the corresponding service routine in normal operation mode. ; The flag responsible for the current ISR call has to be cleared ; to prevent recursive ISR calls. Other interrupt flags, activated ; during execution of this ISR, will immediately be served upon ; termination of the current ISR run. _INCF incf KBDcnt,F ; increment acquisition counter _ISR_RS232error _KBDend bcf INTCON,INTF ; clear RB0/INT interrupt flag ;goto ISRend ; terminate execution of ISR ;***************************************** ;*** ISR TERMINATION (CONTEXT RESTORE) *** ;***************************************** ISRend movfw FSR_TEMP ; context restore movwf FSR ; context restore movfw PCLATH_TEMP ; context restore movwf PCLATH ; context restore swapf STATUS_TEMP,W ; context restore movwf STATUS ; context restore swapf W_TEMP,F ; context restore swapf W_TEMP,W ; context restore RETFIE ; enable global interrupt (INTCON,GIE) ;***** END OF INTERRUPT SERVICE ROUTINE ***** ;***** KEYBOARD SCAN PATTERN DECODING SUBROUTINE ***** KBDdecode ;********************************************************** ;*** KEYBOARD SCAN CODE PRE-DECODING, SET / CLEAR FLAGS *** ;********************************************************** ;*** check key release scan code (F0) *** movfw KBD ; get scan code movwf KBDcopy ; make backup of scan code for later use sublw 0xF0 ; check if FO has been sent: bnz _KBD_1 ; branch if no 'release' scan code occured bsf RELflag ; set key release flag if 'release' occured bcf SPEflag ; clear special code flag always on release goto _ClrStall ; abort with nothing to display _KBD_1 btfss RELflag ; check release flag, exit if cleared: goto _KBD_2 ; release flag has not been set, branch ;*** release flag has been set / key release is in progress: *** bcf RELflag ; clear key release flag ;*** if release of SHIFT key, clear shift flag: *** movfw KBD ; check left shift button (0x12): sublw 0x12 ; subtract, check if zero bz _clrSHI ; if zero, branch movfw KBD ; check right shift button (0x59): sublw 0x59 ; subtract, check if zero skpnz ; skip on non zero _clrSHI bcf SHIflag ; clear shift flag ;*** check for CAPS LOCK activity: *** movfw KBD ; check caps lock key release: sublw 0x58 ; subtract, check if zero bnz _clrALT ; if not zero, branch btfss CAPflag ; check flag, clear flag if set: goto _setCAP ; flag has not been set, branch bcf CAPflag ; clear flag goto _ClrStall ; abort with nothing to display _setCAP bsf CAPflag ; set flag if cleared goto _ClrStall ; abort with nothing to display ;*** check for ALT activity: *** _clrALT movfw KBD ; check ALT key release: sublw 0x11 ; subtract, check if zero bnz _clrCTRL ; if not zero, branch (to next check) bcf ALTflag ; clear flag goto _ALTdec ; goto ALT-DEC-Entry conversion/display routine ; /not implemented, enhancement/ ;*** check for CTRL activity: *** _clrCTRL movfw KBD ; check CTRL key release: sublw 0x14 ; subtract, check if zero bnz _ClrStall ; if not zero, branch / exit bcf CTRLflag ; clear flag goto _CTRLhex ; goto CTRL-HEX-Entry conversion/display routine ; /not implemented, enhancement/ ;**************************************************** ;* The following table has to be located within one * ;* page to allow for correct lookup functionality. * ;* Therefore, additional ISR code has been moved * ;* further down. * ;**************************************************** ;********************************************************************* ;* LOOKUP TABLE FOR KEYBOARD-SCAN-CODE TO ASCII-CHARACTER CONVERSION * ;********************************************************************* ;ORG 0x?? ; if necessary, move table #include "..\tables\eng_main.asm" ; English 'codepage' ;#include "..\tables\ger_main.asm" ; modified Swiss-German 'codepage' ;**************************************************** ;* The following code belongs also to the interrupt * ;* service routine and has been moved down to this * ;* place to allow the main keyboard decode lookup * ;* table to be located within one page. * ;* The code below may be arranged on another page, * ;* but that doesn't matter. * ;**************************************************** ;******************************** ;*** SCAN CODE RANGE CHECKING *** ;******************************** _KBD_2 ;*** check if special code (0xE0) has been submitted previously *** btfss SPEflag goto _KBD_3 ;*** decoding of scan code with preceding special code (0xE0) *** ; (decoding currently only necessary for 'E0 4A' = '/') movfw KBD sublw 0x4A ; 0x4A - w bnz _NOSUP ; branch on non-zero movlw '/' ; store '/' in KBD movwf KBD goto _OUTP _NOSUP ;*** check if scan code 0x5A or smaller has occurred *** movfw KBD sublw 0x5A ; 0x5A - w bc _KBD_3 ; carry if result positive or zero, branch ;*** range exceeded (above 0x5A) *** ; it's one of the following keys: arrow button, 'Home', 'Del', ; 'PageUp', 'PageDown', 'Insert', 'End' ; these keys are currently not used, so goto _ClrStall _KBD_3 ;*** check if scan code 0x61 or smaller has occurred *** movfw KBD sublw 0x61 ; 0x61 - w bc KBD_dec ; carry if result positive or zero, goto table movlw d'14' subwf KBD,F ; KBD = KBD - d'14' ;*** check if scan code 0x61 (0x6F-d'14') or smaller has occurred *** movfw KBD sublw 0x61 ; 0x61 - w bnc _KBD_4 ; no carry if result negative, goto _KBD_4 movlw d'25' addwf KBD,F ; KBD = KBD + d'25' goto KBD_dec _KBD_4 ;*** check if scan code 0x78 (0x86 - d'14') or higher has occurred *** movfw KBD sublw 0x77 ; 0x77 - w bc KBD_dec ; carry if result zero or positive, branch ;*** no character to display: *** ;*** check for special code (0xE0): 0xD2 = 0xE0 - d'14' *** movfw KBD sublw 0xD2 ; 0xD2 - w skpnz ; skip if not zero bsf SPEflag ; special code occurred, set flag goto _ClrStall ; abort with nothing to display ;******************************************************* ;*** SCAN CODE DECODING & ASCII CHARACTER CONVERSION *** ;******************************************************* ;*** DECODE SCAN CODE *** KBD_dec movlw HIGH KBDtable ; get correct page for PCLATH movwf PCLATH ; prepare right page bits for table read movfw KBD call KBDtable ; GET CORRESPONDING KEYBOARD CHAR IN LOOKUP TABLE movwf KBD ; save result to KBD tstf KBD ; test KBD to get the zero flag bz _ClrStall ; abort if KBD is zero / invalid entry, nothing to display ;*** check for ALT-DEC-Entry *** ; /not implemented, enhancement/ ;btfsc ALTflag ; check flag ;goto _ALTstr ; jump if set ;*** check for CTRL-HEX-Entry *** ; /not implemented, enhancement/ ;btfsc CTRLflag ; check flag ;goto _CTRLstr ; jump if set ;*** convert only LETTERS to capital letters: *** ; a letter in KBD value has to be in range from 0x61 to 0x7A movfw KBD sublw 0x60 ; 0x60 - w bc _SHICHR ; carry if result greater or equal zero = no letter, exit movfw KBD sublw 0x7A ; 0x7A - w bnc _SHICHR ; no carry if result negative = no letter, exit ;*** there is now a letter in KBD, check conversion to capital letter: *** movfw KBD btfsc CAPflag ; check caps lock flag goto _SHIset ; flag has been set btfss SHIflag ; check shift flag goto _OUTP ; no flag, exit goto _cnvCAP ; flag has been set, convert to capital letter _SHIset btfsc SHIflag ; check shift flag goto _OUTP ; flag has been set, exit _cnvCAP addlw d'224' ; convert to capital letter (+ d'224') movwf KBD ;goto _OUTP ; (uncomment in case _OUTP will be moved) ;************************************* ;*** KEYBOARD DATA OUTPUT TO RS232 *** ;************************************* _OUTP ;*** RS232 *** movfw KBD SENDw ; send actual pressed keyboard character goto _ClrStall ; (uncomment in case _ClrStall will be moved) ;************************************************ ;*** SPECIAL COMMANDS I (with special output) *** ;************************************************ _CRLF SEND CR ; on 'Enter', send CR and LF to RS232 movlw LF ; put LF to w, return RETURN ;********************************************************** ;*** STALL RELEASE & CLEAR KEYBOARD DATA RECEPTION FLAG *** ;********************************************************** _ClrStall BANK1 bsf KBDclktris ; set clk line back to input (and goes high) BANK0 ; (release stall) bcf KBDflag ; clear keyboard data reception flag bsf INTCON,INTE ; re-enable interrupt RB0/INT RETURN ;**************************************************** ;*** SPECIAL COMMANDS II (without special output) *** ;**************************************************** _SHIFT bsf SHIflag ; set shift flag RETLW 0 ; clear w to obtain invalid entry _ALT bsf ALTflag ; set ALT flag RETLW 0 ; clear w to obtain invalid entry _CTRL bsf CTRLflag ; set CTRL flag RETLW 0 ; clear w to obtain invalid entry ;*********************************************** ;*** ALT-DEC & CTRL-HEX STORING & CONVERSION *** ;*********************************************** ; store typed numbers in CTRLreg1 - CTRLreg3 _CTRLstr ; /not implemented, enhancement/ _ALTstr ; /not implemented, enhancement/ _ALTdec ; PRE: ALT + [1..3] numbers (e.g. ALT + 6 + 4 = @) in CTRLreg1 - 3 ; POST: convert ALT-DEC-Entry after release of ALT key, return ; ascii value converted from numbers ; /not implemented, enhancement/ _CTRLhex ; PRE: CTRL + [1..2] letters/numbers (e.g. CTRL + 3 + F = ?) ; in CTRLreg1 - 2 ; POST: convert ALT-DEC-Entry after release of ALT key, return ; ascii value as concatenated hex value from numbers ; /not implemented, enhancement/ ; catch all handler for non-implemented features: goto _ClrStall ; abort & exit (nothing to display/send) ;***************************************************************** ;*** SCAN CODE DECODING & ASCII CONVERSION FOR 'SHIFT' ENTRIES *** ;***************************************************************** _SHICHR ;*** special character decoding typed with shift button active *** ; check for active shift button, if not active, branch btfss SHIflag goto _OUTP ; branch ; check for 'backspace', 'tab', 'linefeed' and 'carriage return' : ; (here, KBD has already been converted to ASCII character values) movfw KBD sublw d'13' ; d'13' - w bc _OUTP ; carry if result zero or positive, branch ;*** range check: abort if KBDcopy greater than 0x61 *** ; (KBDcopy has the value of the original keyboard scan code) movfw KBDcopy sublw 0x61 ; 0x61 - w bnc _OUTP ; no carry if result negative, branch ;*** check if KBDcopy greater than 0x3C *** movfw KBDcopy sublw 0x3C ; 0x3C - w bc _SHICH1 ; carry if result zero or positive, branch movlw d'61' subwf KBDcopy,F ; KBDcopy = KBDcopy - d'61' goto _SHICH3 ;*** check if KBDcopy greater than 0x24 *** _SHICH1 movfw KBDcopy sublw 0x24 ; 0x24 - w bc _SHICH2 ; carry if result zero or positive, branch movlw d'35' subwf KBDcopy,F ; KBDcopy = KBDcopy - d'35' goto _SHICH3 ;*** else *** _SHICH2 movlw d'4' addwf KBDcopy,F ; KBDcopy = KBDcopy + d'4' _SHICH3 movlw HIGH KBDSHIFTtable ; get correct page for PCLATH movwf PCLATH ; prepare right page bits for table read movfw KBDcopy call KBDSHIFTtable ; GET CORRESPONDING KEYBOARD CHAR IN LOOKUP TABLE movwf KBD ; save result to KBD goto _OUTP ;******************************************************* ;* The following table has also to be located within * ;* one page to allow for correct lookup functionality. * ;******************************************************* ;********************************************************************** ;* LOOKUP TABLE FOR SPECIAL CHARACTERS TYPED WITH SHIFT BUTTON ACTIVE * ;********************************************************************** ;ORG 0x?? ; if necessary, move table #include "..\tables\eng_shif.asm" ; English 'codepage' ;#include "..\tables\ger_shif.asm" ; modified Swiss-German 'codepage' ;***** END OF SCAN PATTERN DECODING SUBROUTINE ***** ;************** MAIN ************** MAIN ORG 0x00 BANK1 clrf OPTION_REG ; PORTB pull-ups enabled goto _MAIN ORG 0x1E0 _MAIN ;*** RS232 INITIALIZATION *** ; Do not call RS232init, since we have no RS232 reception and ; PORTB,0 is already used by the keyboard. ; (Note: KEYBOARDinit and RS232init are almost equal) ; Initialize only RS232 transmission (TXport): bcf TXtris ; set RS232 output BANK0 bsf TXport ; set default state: logical 1 ;*** AT KEYBOARD INITIALIZATION *** KEYBOARDinit ; keyboard initialization clrf KBDcnt ; clear IRQ based scan pattern counter clrf FLAGreg ; clear all flags (keyboard & other) ;*** ENABLE ALL INTERRUPTS *** movlw b'11111000' andwf INTCON,F ; clear all interrupt flags bsf INTCON,GIE ; enable global interrupt ;*** define amount of table items for startup message *** #define tab_items d'42' movlw tab_items ; store amount of table items in counter movwf TEMP3 ;*** transmit startup message *** _ILOOP movlw HIGH WelcomeTable ; get correct page for PCLATH movwf PCLATH ; prepare right page bits for table read movfw TEMP3 ; get actual count-down value sublw tab_items ; table offset: w = tab_items - TEMP3 call WelcomeTable ; call lookup table SENDw decfsz TEMP3,F ; decrement counter goto _ILOOP ;****************************** _MLOOP btfsc KBDflag ; check scan pattern reception flag call KBDdecode ; if set, call decoding routine goto _MLOOP ;****************************** ORG 0x210 ; align table within page WelcomeTable addwf PCL,F ; add offset to table base pointer DT "PIC 16F84 AT Keyboard Decoder connected" ; create table retlw CR ; Carriage Return retlw LF ; Line Feed WTableEND retlw LF ; Line Feed IF (high (WelcomeTable) != high (WTableEND)) ERROR "Welcome table hits page boundary!" ENDIF END