; spam.asm
; Doug Ricket, 6-24-01
;
; This program prints all ascii characters to the serial port


main:

	acall	serialinit	; set up the serial port
	
	
	mainloop:

	mov	a, #'s'		; Load a with the 's' character
	acall	sndchr		; Transmit A through the serial port
	mov	a, #'p'	
	acall	sndchr		
	mov	a, #'a'	
	acall	sndchr		
	mov	a, #'m'	
	acall	sndchr		
	mov	a, #' '	
	acall	sndchr		
	
	sjmp	mainloop	; Local GOTO mainloop


; ******** Support routines are below  ***********

serialinit:
; set up serial port with a 11.0592 MHz crystal,
; use timer 1 for 9600 baud serial communications (19200 for RD2 chip)
   mov   tmod, #20h       ; set timer 1 for auto reload - mode 2
   mov   tcon, #41h       ; run counter 1 and set edge trig ints
   mov   th1,  #0fdh      ; set 9600 baud with xtal=11.059mhz
   mov   scon, #50h       ; set serial control reg for 8 bit data
                          ; and mode 1
   ret

;===============================================================
; subroutine sndchr
; this routine takes the chr in the acc and sends it out the
; serial port.
;===============================================================
sndchr:
   clr  scon.1            ; clear the tx  buffer full flag.
   mov  sbuf,a            ; put chr in sbuf
txloop:
   jnb  scon.1, txloop    ; wait till chr is sent
   ret