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Will Reeve
Joined: 30 Oct 2003
Posts: 209
Location: Norfolk, England
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| PIC12F509 int16 and int8 counter code |
 Posted: Mon May 17, 2010 9:33 am |
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Hi,
with tick defined as a int16 the compiler produces the following code:
| Code: | .................... if (get_timer0()==0) tick++;
0095: MOVF 01,W
0096: BTFSS 03.2
0097: GOTO 09B
0098: INCF 0F,F
0099: BTFSC 03.2
009A: INCF 10,F
.................... if (tick > 270) {
009B: MOVLW 00
009C: MOVWF 07
009D: MOVF 10,W
009E: SUBWF 07,W
009F: BTFSC 03.0
00A0: GOTO 0B1
00A1: XORLW FF
00A2: BTFSS 03.2
00A3: GOTO 0AA
00A4: MOVLW 0E
00A5: MOVWF 07
00A6: MOVF 0F,W
00A7: SUBWF 07,W
00A8: BTFSC 03.0
00A9: GOTO 0B1
.................... output_toggle(LED);
00AA: BCF 0C.0
00AB: MOVF 0C,W
00AC: TRIS 6
00AD: MOVLW 01
00AE: XORWF 06,F |
Looks OK. But doesn't work. With tick an int8 and the check as tick > 245 code works fine:
| Code: | .................... if (get_timer0()==0) tick++;
0093: MOVF 01,W
0094: BTFSC 03.2
0095: INCF 0D,F
.................... if (tick > 245) {
0096: MOVLW F5
0097: MOVWF 07
0098: MOVF 0D,W
0099: SUBWF 07,W
009A: BTFSC 03.0
009B: GOTO 0A2
.................... output_toggle(LED);
009C: BCF 0A.0
009D: MOVF 0A,W
009E: TRIS 6
009F: MOVLW 01
00A0: XORWF 06,F
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What have a overlooked? (please!). WDT is disabled so processor is not resetting. |
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Will Reeve
Joined: 30 Oct 2003
Posts: 209
Location: Norfolk, England
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| Posted: Mon May 17, 2010 9:37 am |
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| I've just narrowed it down. With tick set to an int16 code works as expected with if (tick > 254) but change it to if (tick > 255) which should work with an int16, code breaks! |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon May 17, 2010 12:13 pm |
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What's your compiler version ? I only have vs. 4.073, which is the
version of the free PCB compiler that's bundled with MPLAB v8.46.
I made the following test program and stepped through the code in MPLAB
simulator and it does work. 'result' goes to 0x01 in the Watch Window.
| Code: |
#include <12F509.H>
#fuses INTRC,NOWDT
#use delay(clock=4000000)
//=========================
void main()
{
int8 result;
int16 tick;
result = FALSE;
tick = 300;
if(tick > 255)
result = TRUE;
else
result = FALSE;
while(1);
}
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Here's the .LST file for it. With the comparison to > 255, the compiler
can optimize the test so that it only checks to see if the MSB of 'tick' is
non-zero. If that's the case, then the test is true. You can see them do
that in the code below.
| Code: |
.................... void main()
.................... {
0002: CLRF 04
.................... int8 result;
.................... int16 tick;
....................
....................
.................... result = FALSE;
0003: CLRF 0D
.................... tick = 300;
0004: MOVLW 01
0005: MOVWF 0F
0006: MOVLW 2C
0007: MOVWF 0E
....................
.................... if(tick > 255)
0008: MOVLW 00
0009: MOVWF 07 // Set scratch register to 0x00
000A: MOVF 0F,W // Get MSB of 'tick' into W
000B: SUBWF 07,W // Compare MSB of 'tick' to 0x00
000C: BTFSC 03.0 // Jump if a borrow occurred (ie., if MSB != 0)
000D: GOTO 011
.................... result = TRUE;
000E: MOVLW 01 // If MSB is != 0, then set 'result' = 01 (True)
000F: MOVWF 0D
.................... else
0010: GOTO 012
.................... result = FALSE;
0011: CLRF 0D
....................
.................... while(1);
0012: GOTO 012
.................... }
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Will Reeve
Joined: 30 Oct 2003
Posts: 209
Location: Norfolk, England
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| Posted: Mon May 17, 2010 12:52 pm |
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Mine is version 4.107. Thanks. I've got your code to work (I am using real hardware and an LED as I don't use Mplab, your result variable I changed to a PIN!). I've gone back to the original code and mysteriously the code now works! I don't know why but I am happy! Finger trouble I used to say! I did think I was going insane!
Thanks for you help.
I hadn't realised MPLAB has a simulator....this has turned out to be a good question and answer as I haven't used MPLAB for maybe 10 years! Time to have another look I think as I usually ICD most code development but on these little parts you can't. |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Mon May 17, 2010 3:51 pm |
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The Simulator in MPLAB is great! Too bad you didn't know about this feature as it could have saved you a lot of time.
I often used the included stopwatch for timing measurements, much easier than pulsing an output pin connected to a scope. |
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