On Saturday 07 October 2006 16:13, Scott Dattalo wrote:
>
> I'm really pleased to see that you're using gpsim for your development!
>
Not as pleased as I am to have such a useful tool available. I rather like
the breadboard facility, allows you to see what is happening in real (or
realish) time if you have a lot of long loops.
> The reason gpsim halted is because address 0x90 is invalid for the
> 16F877. The T1CON register (which I assume you're attempting to address)
> is at address 0x10. So the problem is that your bank register is
> incorrect; your pointing into bank 01 when you should be pointing into
> bank 00. I don't know if the offending code was written by you or SDCC,
> but in either case you may track down where the bank was (or was not)
> getting written by using gpsim's trace command. For example, you can say
> 'trace 100' to see what has happened for the last 100 instruction
> cycles. This will allow you to inspect where things went awry.
The offending assembly code was written by by sdcc from my C, the routine
stops in a software serial port driver bit of code, from looking at the
source browser (I know most pics nowadays have USARTS but I thought it
would be better to have a software solution working first).
However, this code has been fine earlier, it has been working on my
pic16f877 development board for over a week when used with other routines.
My assumption is that the use of more variables in other bits of code has
caused sdcc to move one of the variables used by the serial routine into a
place it should not have.
Note I've been a bit lazy with my delay routine, basically estimating the
delays by viewing the resultant RS232 signals on a scope. I should have
produced the delay using in-line assembly so I knew exactly what the
delays were! I've left all the comments just in-case I've made a boo-boo
there!
C:
void Half_Bit_Delay(void) {
unsigned char loop;
//OK, PIC clocking at 20MHz
// /4 = 5MHz
// 200nsec per instruction
// If we go for 19200 baud
//52 instruction pause
//assume loop takes 2, 26, but half bit, 13
// assume 4 instruction overhead
//9
//Go for 9600 baud delay of 128
//With 128 1.5msec for 10 bits worth, start 8 stop
//That gives a baud rate of 1.5 e -03 / 10 equates
//to 6667 baud
//Correct ! 128 * 6667 / 9600 = 89!
//Which gives 8333 baud!
//Tweek slihtly faster
for (loop = 0; loop < 79 ; loop++ ) {
}
}
Assembly produced by sdcc, gpsim freezes where marked:
;***
; pBlock Stats: dbName = C
;***
;entry: _Half_Bit_Delay ;Function start
; 2 exit points
;has an exit
;1 compiler assigned register :
; r0xB0
;; Starting pCode block
_Half_Bit_Delay ;Function start
; 2 exit points
; .line 103; "../plibpic/serial/serial-sw-2006-10-5.h" for (loop = 0;
loop
< 79 ; loop++ ) {
MOVLW 0x4f
BANKSEL r0xB0
MOVWF r0xB0
_00115_DS_
DECFSZ r0xB0,F
GOTO _00115_DS_ <----- GPSIM seems to stop here!
RETURN
; exit point of _Half_Bit_Delay
All a bit odd though, as the routine works for a while before it bangs out.
Also, I though sdcc insulated me from setting bank bits? Also a bit
perplexed.
Hmm, a lot of code playing around at 0x90 from elsewhere in my serial
routine, a code snippet. Looks like it would be valid if the pic is
working in banks 2 or 3 but from the error message I would assume it is in
bank 0? I'm a bit confused by the 'BANKSEL' instruction, I assume it is
some sort of assembler macro rather than a PIC instruction.
; .line 257; "../plibpic/serial/serial-sw-2006-10-5.h"
serialbuff[serialbuff_index] = in;
BANKSEL _serialbuff_index
MOVF _serialbuff_index,W
ADDLW (_serialbuff + 0)
MOVWF r0x90
MOVLW high (_serialbuff + 0)
BTFSC STATUS,0
ADDLW 0x01
MOVWF r0x91
MOVF r0x90,W
MOVWF FSR
BCF STATUS,7
BTFSC r0x91,0
BSF STATUS,7
MOVF r0x8F,W
MOVWF INDF
I need to RTFM a bit on trace, I seem either to get the last instruction or
a lot of short lines of hex!
Pete
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