Andrew Warren wrote:

> Mark Dennehy <PICLIST@MITVMA.MIT.EDU> wrote:
>
> > Has anyone using an ICEPIC come across the problem of having some
> > registers act funnily ? (ie. not incrementing on an INCF
> > <register>,F and then later returning absurd values ???)
>
> Mark:
> It could be an ICEPIC bug, but before you make that assumption, you
> should check to be SURE that:
>     1.  You've actually loaded the ICEPIC's program memory with the
>         program whose source code you're single-stepping through.

That would sound funny to me if I hadn't done that three times over the
last month ... :)

>     2.  The correct register-page is selected when your "INCF" is
>         executed.

Yes, it's relocatable code and there's a BANKSEL statement in front of
it, as shown at the end of this message.

>      3.  An interrupt is corrupting the register in question.

That's something I though might be happening, but I've single-stepped
thgough the code and the interrupts don't do anything to the value in
temp.

Here's the relevant code :

USART_TEMP  UDATA
temp   RES 1

;--------------------ROUTINE SPECIFICATION-------------------
;
; NAME :   USART_puts
;
; FUNCTION :  Takes a string in ROM and sends it
;     down the serial line
;
; INPUTS :  The address of the string in USART_hi_msg_tmp
;     and USART_lo_msg_tmp.
;
; OUTPUTS :  W is 0 if successful, otherwise W holds
;     an errorcode
;
; CALLS :   USART_putc
;     USART_message_table
;
; CALLED BY :
;
; NOTES :
;
;------------------------------------------------------------
; REVISION HISTORY :
;
;------------------------------------------------------------


;USART_PUTS
; Move the address of the string table into a temporary pointer.
USART_puts  CODE
USART_puts
    GLOBAL USART_puts

    EXTERN USART_hi_msg_tmp
    EXTERN USART_lo_msg_tmp
    EXTERN USART_message_table

 BANKSEL temp
 clrf temp

; Get the character at that address,

USART_puts_loop
 PAGESEL USART_message_table
 movf temp,W
 call USART_message_table

; If the character is not a NUL,

 xorlw 0
 btfsc STATUS,Z
 goto USART_puts_msgdone
 movwf tmpchar

;  putc that character,

 PAGESEL USART_putc
 movf tmpchar,W
 call USART_putc

;  increment the pointer and reloop

 BANKSEL temp
 incf temp,F
 goto USART_puts_loop

; if the character is a NUL, that's the end of the string,
; so clear temp and return 0

USART_puts_msgdone

 retlw 0

--
Mark Dennehy, B.A., B.A.I.  Email : Mark.Dennehy@cs.tcd.ie
Research Student,
Computer Vision and Robotics Research Group,
Computer Science Dept., Trinity College Dublin