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Marko
Joined: 02 Jul 2007
Posts: 3
Location: New Zealand
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| PIC16F628A comparator annoyance |
 Posted: Mon Jul 02, 2007 9:43 pm |
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My program includes the command "setup_comparator(A0_VR_A1_VR)". When I look at the .lst file it has been translated into...
MOVLW 02
BSF 03.5
MOVWF 30
MOVF 05,W
IORLW 03
MOVWF 05
MOVLW 03
MOVWF 77
01A:DECFSZ 77,F
GOTO 01A
BCF 03.5
MOVF 63,W
BCF 0C.6
I would have thought that this command would have set CMCON (at 1F) to 2, ie enabling the comparators for operation with vref. Instead, the comparators are not enabled and the circuit does not function. I have to manually set CMCON for the comparators to work. Why does the compiler work like this? What am I missing here?? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Jul 02, 2007 10:25 pm |
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| On a question like this, you need to post your compiler version. |
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Marko
Joined: 02 Jul 2007
Posts: 3
Location: New Zealand
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| Posted: Mon Jul 02, 2007 10:50 pm |
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| Version 4.027 |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Jul 02, 2007 11:45 pm |
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Your version is buggy. It's using the wrong address for CMCON.
This is what is it looks like in 3.249. This is correct code:
| Code: |
.................... void main()
.................... {
0004: CLRF 04
0005: MOVLW 1F
0006: ANDWF 03,F
0007: MOVLW 07
0008: MOVWF 1F // CMCON = 0x07
.................... setup_comparator(A0_VR_A1_VR);
0009: MOVLW 02
000A: MOVWF 1F // CMCON = 0x02
000B: BSF 03.5 // Bank 1
000C: MOVF 05,W
000D: IORLW 03 // Set Pins A0 and A1 = inputs
000E: MOVWF 05
000F: MOVLW 03 // Delay 10 us
0010: MOVWF 77
0011: DECFSZ 77,F
0012: GOTO 011
0013: BCF 03.5 // Bank 0
0014: MOVF 1F,W // Read CMCON
0015: BCF 0C.6 // Clear CMIF bit in PIR1
....................
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Here's the code with vs. 4.042. It's also correct. They added one
thing -- they're clearing the IRP bit in the start-up code.
| Code: |
.................... void main()
.................... {
0004: CLRF 04
0005: BCF 03.7
0006: MOVLW 1F
0007: ANDWF 03,F
0008: MOVLW 07
0009: MOVWF 1F
.................... setup_comparator(A0_VR_A1_VR);
000A: MOVLW 02
000B: MOVWF 1F
000C: BSF 03.5
000D: MOVF 05,W
000E: IORLW 03
000F: MOVWF 05
0010: MOVLW 03
0011: MOVWF 77
0012: DECFSZ 77,F
0013: GOTO 012
0014: BCF 03.5
0015: MOVF 1F,W
0016: BCF 0C.6
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So, it's clear that in going to vs. 4, the code generator or the Device Data
got broken for the setup_comparator() function for the 16F628A.
Sometime after vs. 4.027, they fixed it. You can contact CCS support
and ask them (politely) what they will do about it. Maybe they will
upgrade you to a working version. You'll have to ask them. |
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Marko
Joined: 02 Jul 2007
Posts: 3
Location: New Zealand
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| Posted: Tue Jul 03, 2007 1:29 am |
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I had spent umpteen hours trying to find the problem in hardware, thinking that there could never be a compiler issue. I'm too used to programming in other environments where compiler issues are as rare as hen's teeth. Hopefully CCS will listen to my plea/whining for an upgrade.
Thanks for that PCM-P. You seem to be a hard working person, answering everyone's questions! Have a pat on the back from me. |
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