Why does my PIC skip GOTO ? What could be wrong ?

[nurquhar]

I have some simple code that the complier (V3.249) is generating GOTO's to implement (even though I have used #separate for the function call!). The source code and assembley below.

I am using Microchip ICD2 to trace the code on a PIC16F648_ICD chip plugged into may target.

If I set a breakpoint on a NOP before or after the check_rx() and run the traget it will halt at the expected instruction. If I move the break point to the NOP at the begining of the check_rx() function and run the traget from the beginning again then the break point is never reached !!

What is realy unexplainable is if I single step (step into) through this bit of code in main()

0460: NOP
.................... nop() ;
0461: NOP
.................... check_rx() ;
0462: GOTO 3B7
.................... nop() ;
0463: NOP

then it never does the GOTO 3B7 it just steps to the next NOP at 0463.

If I carry on single stepping it also fails to do the GOTO 45F and effectivley exits the while(1) {} loop, it runs through the GOTO at the end of main loop also, ie its crashed !!

0463: NOP
.................... nop() ;
0464: NOP
.................... nop() ;
0465: NOP
.................... }
0466: GOTO 45F
....................


The source ..........................................................
..................................

#separate
void check_rx()
{
char ch ;

nop() ;
nop() ;
nop() ;

// Check for overrun error
if (OERR) {
// Clear the error
CREN = 0 ;
CREN = 1 ;
mstcp_rawin(0, MSTCP_OVERRUN_ERR) ;
}

nop() ;
nop() ;
nop() ;

// Check for framing error
if (FERR) { \
ch=RCREG ;
mstcp_rawin(ch, MSTCP_FRAME_ERR) ;
}

nop() ;
nop() ;
nop() ;

// Check for command
if(kbhit()) {
ch = getc() ;
mstcp_rawin(ch, MSTCP_DATA_RX) ;
}

nop() ;
nop() ;
nop() ;
}
.

.
main()
{
.
.
.

while(1) {
nop() ;
nop() ;
nop() ;
check_rx() ;
nop() ;
nop() ;
nop() ;
}


......................................................................................................
.........................................................................
The relavant snippets are from the LST file are :

CCS PCM C Compiler, Version 3.249, 33800 08-Aug-06 08:57

Filename: LinLED_01.lst

ROM used: 1137 words (30%)
Largest free fragment is 1792
RAM used: 63 (38%) at main() level
89 (53%) worst case
Stack: 6 worst case (5 in main + 1 for interrupts)

*
0000: NOP
0001: MOVLW 00
0002: MOVWF 0A
0003: GOTO 3E0

.
.

....................
....................
.................... #separate
.................... void check_rx()
.................... {
.................... char ch ;
....................
.................... nop() ;
*
03B7: NOP
.................... nop() ;
03B8: NOP
.................... nop() ;
03B9: NOP
....................
.................... // Check for overrun error
.................... if (OERR) {
03BA: BTFSS 18.1
03BB: GOTO 3C2
.................... // Clear the error
.................... CREN = 0 ;
03BC: BCF 18.4
.................... CREN = 1 ;
03BD: BSF 18.4
.................... mstcp_rawin(0, MSTCP_OVERRUN_ERR) ;
03BE: CLRF 5E
03BF: MOVLW 87
03C0: MOVWF 5F
03C1: CALL 238
.................... }
....................
.................... nop() ;
03C2: NOP
.................... nop() ;
03C3: NOP
.................... nop() ;
03C4: NOP
....................
.................... // Check for framing error
.................... if (FERR) { \
03C5: BTFSS 18.2
03C6: GOTO 3CE
.................... ch=RCREG ;
03C7: MOVF 1A,W
03C8: MOVWF 5D
.................... mstcp_rawin(ch, MSTCP_FRAME_ERR) ;
03C9: MOVF 5D,W
03CA: MOVWF 5E
03CB: MOVLW 86
03CC: MOVWF 5F
03CD: CALL 238
.................... }
....................
.................... nop() ;
03CE: NOP
.................... nop() ;
03CF: NOP
.................... nop() ;
03D0: NOP
....................
.................... // Check for command
.................... if(kbhit()) {
03D1: BTFSS 0C.5
03D2: GOTO 3DB
.................... ch = getc() ;
03D3: BTFSS 0C.5
03D4: GOTO 3D3
03D5: MOVF 1A,W
03D6: MOVWF 5D
.................... mstcp_rawin(ch, MSTCP_DATA_RX) ;
03D7: MOVF 5D,W
03D8: MOVWF 5E
03D9: CLRF 5F
03DA: CALL 238
.................... }
....................
.................... nop() ;
03DB: NOP
.................... nop() ;
03DC: NOP
.................... nop() ;
03DD: NOP
.................... }
03DE: BCF 0A.3
03DF: GOTO 463 (RETURN)
....................

.
.

....................
.................... while(1) {
.................... nop() ;
045F: NOP
.................... nop() ;
0460: NOP
.................... nop() ;
0461: NOP
.................... check_rx() ;
0462: GOTO 3B7
.................... nop() ;
0463: NOP
.................... nop() ;
0464: NOP
.................... nop() ;
0465: NOP
.................... }
0466: GOTO 45F
....................

[PCM programmer]

You should ask this question in the Microchip ICD2 forum.
It might be some issue with the 16F648A-ICD header.
http://forum.microchip.com/tt.aspx?forumid=49