Hi all. I've just built a little 16f876a based surface mount board
with a MAX233 convertor. The idea is that I'm going to load it up with
a bootloader so I don't have to lug my programmer with me while I'm on
vacation next week (yes, I work during my vacations). I wrote up the
following little program to test that the RS232 connection is working.
I've never used a bootloader before, so I just wanted to verify my
hardware first. However, it isn't working. I've checked my circuit,
and I think I'm ok. I scope the TX line on my PIC and get no activity.
The program turns on port pins as it goes so I can see the progress,
and it seems to get caught in the loop waiting for PIR1, TXIF to go
high (porta,2 never gets set). So...I think I've done something funky
in software. The main guts of this program used to work on a non A
16f876. Maybe that's the key? I thought I had changed the relevant
bits. Maybe I should be looking for the TXSTA, TRMT bit instead of the
TXIF bit? Maybe I've done something stupid and forgotten a bank
switch?

Here is my code...I'd appreciate it if someone could have a look. I
know it isn't the best practice. It's in absolute mode, and it doesn't
use interrupts. Bank switching is messy. The main goal is just to sit
there spewing out data though. Here it is:



	LIST    R=DEC		;  
 	list P=PIC16F876a
	#include p16F876a.inc


		__CONFIG (_HS_OSC & _WDT_OFF & _CP_OFF & _LVP_OFF & _PWRTE_ON &
_BODEN_OFF )	;  #### - Updated

Start_Vector	       EQU     H'00'
Interrupt_Vector       EQU     H'04'
Ram_Base               EQU     H'20'
Common_Ram_Base        EQU     H'70' 

Osc_Freq               EQU     D'16000000'

    CBLOCK Ram_Base
    temp  
    endc


;
; -----------
; DESCRIPTION
; -----------
;
; Baud Rate = 9600, No Parity, 8 bits & 1 Stop Bit
;
; -------------
; PROGRAM START
; -------------
;
    org     Start_Vector
    goto    Start
    

    org     Interrupt_Vector      
    goto    ISR_Start

ISR_Start
    retfie
    


Start
    bcf     status, rp0
    bcf     status, rp1
    clrf    PORTA               ; Clear the ports
    clrf    PORTB
    clrf    PORTC

    bsf     status, rp0         ; Bank 1

    movlw   b'01000110'         ; Setup ADC, All digital
    movwf   ADCON1^ 0x080     
    
    movlw   b'01011111'         ; PortB pullups on
    movwf   OPTION_REG^ 0x080    

    movlw   b'00000000'         ; Setup port directions
    movwf   TRISA^ 0x080
    movlw   b'00000000'
    movwf   TRISB^ 0x080
    movlw   b'11000000'         ; set RC6 & RC7 as input
    movwf   TRISC^ 0x080
    
    bcf     status, rp0         ; Bank 0


; Setup UART

    bsf     status, rp0         ; Bank 1

                    ;  Baud Values with BRGH = 1
                    ;  ((16000000/9600)/16)-1 = 103
    movlw   d'103'              ;  9600 baud @ 16 Mhz Fosc +0.16 err
    movwf   SPBRG^ 0x080
    movlw   b'00100100'         ; brgh = 1
    movwf   TXSTA^ 0x080               ; enable Async Transmission, set brgh

    bcf     status, rp0         ; Bank 0

; ------------------------------------
; PROVIDE A SETTLING TIME FOR START UP
; ------------------------------------
;
    clrf    temp
Settle
    decfsz  temp,f
    goto    Settle

    goto    Main
    
    
Main

	bsf		porta, 0
	movlw	b'10101010'
	movwf	PORTB


    movlw   b'00001010'
    movwf   portc

    movlw   'T'
    call    TXLoop
    movlw   'E'
    call    TXLoop
    movlw   'S'
    call    TXLoop
    movlw   'T'
    call    TXLoop
    movlw   ' '
    call    TXLoop
    goto    Main

TxLoop
    nop

	bsf		porta, 1

    movwf   TXREG

	nop
	nop

    btfss   PIR1,TXIF           ;xmit buffer empty?
    goto    TxLoop              ;no, wait


	bsf		porta, 2

    return

end
 
Thanks for reading this far!

Josh
-- 
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
        -Douglas Adams

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