wrong dispatcher code

[tipoldo]

Hi,
I'm using the CCS PCM C Compiler Version 3.236 on a PIC 16F690. I have to use the comp2_isr in my code to implement a project. I get crazy because sometimes the program had really strange behaviour. Analyzing and tracing the assembler code, I found that the compiler doesn't restore the W register well on interrupt return. Here is the interrupt dispatcher code that the CCS generates in my code:

0003: NOP
0004: MOVWF 7F
0005: SWAPF 03,W
0006: CLRF 03
0007: MOVWF 26
0008: MOVF 7F,W
0009: MOVWF 25
000A: MOVF 0A,W
000B: MOVWF 2D
000C: CLRF 0A
000D: SWAPF 25,F
000E: MOVF 04,W
000F: MOVWF 27
0010: MOVF 20,W
0011: MOVWF 28
0012: MOVF 21,W
0013: MOVWF 29
0014: MOVF 22,W
0015: MOVWF 2A
0016: MOVF 23,W
0017: MOVWF 2B
0018: MOVF 24,W
0019: MOVWF 2C
001A: BCF 03.7
001B: BCF 03.5
001C: MOVLW 8D
001D: MOVWF 04
001E: BTFSS 00.6
001F: GOTO 022
0020: BTFSC 0D.6
0021: GOTO 035
0022: MOVF 27,W
0023: MOVWF 04
0024: MOVF 28,W
0025: MOVWF 20
0026: MOVF 29,W
0027: MOVWF 21
0028: MOVF 2A,W
0029: MOVWF 22
002A: MOVF 2B,W
002B: MOVWF 23
002C: MOVF 2C,W
002D: MOVWF 24
002E: MOVF 2D,W
002F: MOVWF 0A
0030: SWAPF 26,W
0031: MOVWF 03
0032: SWAPF 7F,F
0033: SWAPF 7F,W
0034: RETFIE

Highlighted in red is the code where the compiler save the W register, watching it, it saves the W register in the 0x25 register and swaps it. To do it, the compiler use a temporal register (0x7F). But when the compiler wanted to restore the W register, it is restored with the value of the 0x7F register (highlighted in blue color) instead of the 0x25 register. Unfortunately the compiler uses the temporal 0x7F register into my interrupt function as a register for temporal variable, and therefore the code doesn't restore right the W register when I come back from the interrupt function.

To continue with my project, as a workaround, I have written the following assembler code at the end of the interrupt function comp2_isr():

#ASM
SWAPF 0x25,W
MOVWF 0x7F
#ENDASM

But I don't like it. How can I resolve it?

[SherpaDoug]

What compiler version are you using, and have you informed CCS about this? They don't always monitor this BBS.
_________________
The search for better is endless. Instead simply find very good and get the job done.

[tipoldo]

I'm using the PCM Version 3.236, and I haven't informed about this to CCS yet. Where should I do that?

[SherpaDoug]

At the top of this page near the CCS logo is a link to "Official CCS Support"
Then at the right under Quick Links they tell you how to get official support.
_________________
The search for better is endless. Instead simply find very good and get the job done.