; CC5X Version 3.1G, Copyright (c) B Knudsen Data
; C compiler for the PICmicro family
; ************  28. Mar 2003  10:02  *************

        processor  16C54
        radix  DEC

TMR0        EQU   0x01
PCL         EQU   0x02
PORTA       EQU   0x05
Carry       EQU   0
Zero_       EQU   2
RS232_out   EQU   0
RS232_in    EQU   1
bitCount    EQU   0x0A
limit       EQU   0x0B
serialData  EQU   0x0C
dout        EQU   0x08
ti          EQU   0x09
i           EQU   0x07

  ; FILE test\serial.c
                        ;/*
                        ;  SERIAL COMMUNICATION (RS232)
                        ;  ============================
                        ;
                        ;  Using 9600 baud, one stop bit, no parity.
                        ;  Baudrate 9600 baud => 104.167 microsec. per bit
                        ;  TMR0 counts each 8th microsec. => 13.02 steps per bit
                        ;*/
                        ;
                        ;#define _4_MHz    /* 4 MHz system clock */
                        ;
                        ;#pragma bit RS232_out @ PORTA.0
                        ;#pragma bit RS232_in  @ PORTA.1
                        ;
                        ;#ifdef _4_MHz
                        ; #define   TimeStartbit    4
                        ; #define   BitTimeIncr     13
                        ;#endif
                        ;
                        ;char bitCount, limit;
                        ;char serialData;
                        ;
                        ;#ifdef _4_MHz
                        ; #ifdef UseTMR0
                        ;   #define delayStart   limit = TMR0;
                        ;   #define delayOneBit      \
                        ;     limit += BitTimeIncr;  \
                        ;     while ( limit != TMR0) \
                        ;         ;
                        ; #else
                        ;   #define delayStart   /* empty */
                        ;   #define delayOneBit  {      \
                        ;        char ti;               \
                        ;        ti = 30;               \
                        ;        do ; while( --ti > 0); \
                        ;        nop();                 \
                        ;     }  /* total: 5 + 30*3 - 1 + 1 + 9 \
                        ;           = 104 microsec. at 4 MHz */
                        ; #endif
                        ;#endif
                        ;
                        ;void sendData( char dout)
                        ;/* sends one byte */
                        ;{
sendData
        MOVWF dout
                        ;    RS232_out = 0;  /* startbit */
        BCF   0x05,RS232_out
                        ;    delayStart
                        ;    for ( bitCount = 9; ; bitCount--)  {
        MOVLW .9
        MOVWF bitCount
                        ;        delayOneBit
m001    MOVLW .30
        MOVWF ti
m002    DECFSZ ti,1
        GOTO  m002
        NOP  
                        ;        if ( bitCount == 0)
        MOVF  bitCount,1
        BTFSC 0x03,Zero_
                        ;            break;
        GOTO  m003
                        ;        Carry = 1;  /* incl. stopbit */
        BSF   0x03,Carry
                        ;        dout = rr( dout);
        RRF   dout,1
                        ;        RS232_out = Carry;
        BTFSS 0x03,Carry
        BCF   0x05,RS232_out
        BTFSC 0x03,Carry
        BSF   0x05,RS232_out
                        ;    }
        DECF  bitCount,1
        GOTO  m001
                        ;}
m003    RETLW .0
                        ;
                        ;#define NText 12
                        ;char text( char W)
                        ;{
text
                        ;    skip(W);
        ADDWF PCL,1
                        ;   #pragma return[NText] = "Hello world!"
        RETLW .72
        RETLW .101
        RETLW .108
        RETLW .108
        RETLW .111
        RETLW .32
        RETLW .119
        RETLW .111
        RETLW .114
        RETLW .108
        RETLW .100
        RETLW .33
                        ;}
                        ;
                        ;
                        ;void main( void)
                        ;{
main
                        ;    char i;
                        ;
                        ;    PORTA = 0x03; // xxxx xx11
        MOVLW .3
        MOVWF PORTA
                        ;    TRISA = 0xFE; // xxxx xx10
        MOVLW .254
        TRIS  PORTA
                        ;    OPTION = 2;   // prescaler divide by 8
        MOVLW .2
        OPTION
                        ;
                        ;    for ( i = 0; i < NText; i++)
        CLRF  i
m004    MOVLW .12
        SUBWF i,W
        BTFSC 0x03,Carry
        GOTO  m005
                        ;        sendData( text(i));  /* text string */
        MOVF  i,W
        CALL  text
        CALL  sendData
        INCF  i,1
        GOTO  m004
                        ;
                        ;  WaitNextIO:
                        ;    while ( RS232_in == 1)
m005    BTFSC 0x05,RS232_in
                        ;        ;
        GOTO  m005
                        ;
                        ;  Start_RS232:
                        ;    /* sampling once per bit */
                        ;    TMR0 = 0;
        CLRF  TMR0
                        ;    limit = TimeStartbit;
        MOVLW .4
        MOVWF limit
                        ;    while ( limit != TMR0)
m006    MOVF  limit,W
        XORWF TMR0,W
        BTFSS 0x03,Zero_
                        ;        ;
        GOTO  m006
                        ;    if ( RS232_in == 1)
        BTFSC 0x05,RS232_in
                        ;        goto StartBitError;
        GOTO  m005
                        ;
                        ;    bitCount = 8;
        MOVLW .8
        MOVWF bitCount
                        ;    do  {
                        ;        limit += BitTimeIncr;
m007    MOVLW .13
        ADDWF limit,1
                        ;        while ( limit != TMR0)
m008    MOVF  limit,W
        XORWF TMR0,W
        BTFSS 0x03,Zero_
                        ;            ;
        GOTO  m008
                        ;        Carry = RS232_in;
        BCF   0x03,Carry
        BTFSC 0x05,RS232_in
        BSF   0x03,Carry
                        ;        serialData = rr( serialData);  /* rotate carry */
        RRF   serialData,1
                        ;    } while ( -- bitCount > 0);
        DECFSZ bitCount,1
        GOTO  m007
                        ;
                        ;    limit += BitTimeIncr;
        MOVLW .13
        ADDWF limit,1
                        ;    while ( limit != TMR0)
m009    MOVF  limit,W
        XORWF TMR0,W
        BTFSS 0x03,Zero_
                        ;        ;
        GOTO  m009
                        ;    if ( RS232_in == 0)
        BTFSC 0x05,RS232_in
        GOTO  m005
                        ;        goto StopBitError;
                        ;
                        ;    /* 'serialData' can be processed here */
                        ;    /* NOTE: limited time (40 - 50 microsec.) */
                        ;    goto WaitNextIO;
                        ;
                        ;  StopBitError:
                        ;    /* RS232 stopbit error,
                        ;       waiting while line is low */
                        ;    while ( RS232_in == 0)
m010    BTFSC 0x05,RS232_in
        GOTO  m005
                        ;        ;
        GOTO  m010
                        ;  StartBitError:
                        ;    goto WaitNextIO;
                        ;}

        ORG 0x01FF
        GOTO main
        END


; *** KEY INFO ***
; RAM usage: 6 bytes (3 local), 19 bytes free
; Maximum call level: 1
; Total of 87 code words (16 %)

;    21 word(s),  4 %: sendData
;    13 word(s),  2 %: text
;    52 word(s), 10 %: main