;******************************************************************* 
; Function:  Sends alive message, then echoes characters at 9600 bps 
; Processor: PIC16F628 at 4 MHz using internal RC oscillator 
; Hardware:  Testboard K4 
; Filename:  628uart.asm 
; Author:    Lars Petersen, oz1bxm@qsl.net 
; Website:   www.qsl.net/oz1bxm/PIC/pic.htm 
; Credit:    Tony Nixon's test program at 
;            www.piclist.com/techref/microchip/16f877/setup.htm 
;******************************************************************* 

        LIST P=16F628, R=DEC    ; Use the PIC16F628 and decimal system 

        #include "P16F628.INC"  ; Include header file 

        __config  _INTRC_OSC_NOCLKOUT & _LVP_OFF & _MCLRE_OFF & _WDT_OFF & _PWRTE_ON & _BODEN_OFF

        CBLOCK 0x20             ; Declare variable addresses starting at 0x20 
          dataL 
        ENDC 

        ORG    0x000            ; Program starts at 0x000 
; 
; -------------------------------- 
; SET ANALOG/DIGITAL INPUTS PORT A 
; -------------------------------- 
; 
        movlw 7 
        movwf CMCON             ; CMCON=7 set comperators off 
; 
; ---------------- 
; INITIALIZE PORTS 
; ---------------- 
; 
        movlw b'00000000'       ; set up portA 
        movwf PORTA 

        movlw b'00000100'       ; RB2(TX)=1 others are 0 
        movwf PORTB 

        bsf STATUS,RP0          ; RAM PAGE 1 

        movlw 0xFF 
        movwf TRISA             ; portA all pins input 

        movlw b'11110010'       ; RB7-RB4 and RB1(RX)=input, others output 
        movwf TRISB 

; ------------------------------------ 
; SET BAUD RATE TO COMMUNICATE WITH PC 
; ------------------------------------ 
; Boot Baud Rate = 9600, No Parity, 1 Stop Bit 
; 
        movlw 0x19              ; 0x19=9600 bps (0x0C=19200 bps) 
        movwf SPBRG 
        movlw b'00100100'       ; brgh = high (2) 
        movwf TXSTA             ; enable Async Transmission, set brgh 

        bcf STATUS,RP0          ; RAM PAGE 0 

        movlw b'10010000'       ; enable Async Reception 
        movwf RCSTA 
; 
; ------------------------------------ 
; PROVIDE A SETTLING TIME FOR START UP 
; ------------------------------------ 
; 
        clrf dataL 
settle
        decfsz dataL,F 
        goto settle 

        movf RCREG,W 
        movf RCREG,W 
        movf RCREG,W            ; flush receive buffer 
; 
; --------- 
; MAIN LOOP 
; --------- 
; 
        call message            ; send "16F628 alive" 
loop
        call receive            ; wait for a char 
        call send               ; send the char 
        goto loop 
; 
; ------------------------------------------- 
; RECEIVE CHARACTER FROM RS232 AND STORE IN W 
; ------------------------------------------- 
; This routine does not return until a character is received. 
; 
receive btfss PIR1,RCIF         ; (5) check for received data 
        goto receive 

        movf RCREG,W            ; save received data in W 
        return 
; 
; ------------------------------------------------------------- 
; SEND CHARACTER IN W VIA RS232 AND WAIT UNTIL FINISHED SENDING 
; ------------------------------------------------------------- 
; 
send
        movwf TXREG             ; send data in W 

TransWt
        bsf STATUS,RP0          ; RAM PAGE 1 
WtHere
        btfss TXSTA,TRMT        ; (1) transmission is complete if hi 
        goto WtHere 

        bcf STATUS,RP0          ; RAM PAGE 0 
        return 
; 
; ------- 
; MESSAGE 
; ------- 
; 
message
        movlw  '1' 
        call send 
        movlw  '6' 
        call send 
        movlw  'F' 
        call send 
        movlw  '6' 
        call send 
        movlw  '2' 
        call send 
        movlw  '8' 
        call send 
        movlw  ' ' 
        call send 
        movlw  'a' 
        call send 
        movlw  'l' 
        call send 
        movlw  'i' 
        call send 
        movlw  'v' 
        call send 
        movlw  'e' 
        call send 
        movlw  0x0D ; CR 
        call send 
        movlw  0x0A ; LF 
        call send 
        return 

        END