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ilker07
Joined: 03 Jun 2022
Posts: 32
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| ccs c cannot change wdt prescaler at a run time |
 Posted: Thu Dec 15, 2022 1:51 am |
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Hi everyone,
I'm getting error "Can not change WDT prescale at run-time" when calling setup_wdt(WDT_2S).
The code:
| Code: |
#include <18F67K22.h>
#fuses WDT_SW
#FUSES NOWDT //Watch Dog Timer
#FUSES NOXINST //Extended set extension and Indexed Addressing mode disabled (Legacy mode)
#FUSES NOBROWNOUT //No brownout reset
#use delay(internal=8000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, stream=RS485, errors)
unsigned int16 a=0;
void main()
{
output_high(pin_c5);//RS485
delay_ms(1000);
fprintf(RS485,"Start\n");
setup_wdt(WDT_ON | WDT_2S);
while(TRUE)
{
a++;
fprintf(RS485,"a:%lu\n",a);
restart_wdt();
delay_ms(500);
}
}
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It works with WDT_1S but this way it doesn't even compile. What is the problem? I use 5.015 version. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Dec 15, 2022 2:42 am |
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I installed CCS vs. 5.015 and it compiles your code with no errors or warnings.
| Quote: | Executing: "C:\...\PICC\Ccsc.exe" +FH "PCH_Test.c" +DF +LY -T -A +M -Z +Y=9 +EA #__18F67K22=TRUE
Memory usage: ROM=0% RAM=0% - 0%
0 Errors, 0 Warnings.
Build Successful.
Loaded C:\Program Files\PICC\Projects\PCH_Test\PCH_Test.cof.
BUILD SUCCEEDED: Thu Dec 15 00:40:51 2022
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| Quote: | CCS PCH C Compiler, Version 5.015, xxxxx 15-Dec-22 00:40
Filename: C:\Program Files\PICC\Projects\PCH_Test\PCH_Test.lst
ROM used: 434 bytes (0%)
Largest free fragment is 65536
RAM used: 8 (0%) at main() level
16 (0%) worst case
Stack used: 1 locations
Stack size: 31
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Ttelmah
Joined: 11 Mar 2010
Posts: 19540
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| Posted: Thu Dec 15, 2022 2:45 am |
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Because you can't.
The watchdog prescaler is set in the fuses.
If you code with the line:
setup_wdt(WDT_ON | WDT_2S);
then look at the list file at the fuses, you will see they are set for 2 seconds.
recompile the same code but change it to say 1 sec, and the only thing that
will change in the resulting listing, is the fuses. So from WDT512 to
WDT256.
The C line here is rather misleading. Parts of it (the part that turns the
WDT on/off), code as a line in the assembler. However the watchdog 'time'
just determines the fuse settings, so can only be set _once_ in any
program. You cannot change the watchdog time (on these chips), except
in the fuses. So the time can only be set once.
In the manual:
"Some parts do not allow the time to be changed at run time". This chip
is one of those.
I suspect PCM, he has got two time lines in the code that actually fails.
What he posted works, but if he tries to _change_ the time somewhere
in the code, it won't. So his actual failing code probably has another
line setting the time to 1Sec.
So if he has:
| Code: |
setup_wdt(WDT_1S);
output_high(pin_c5);//RS485
delay_ms(1000);
fprintf(RS485,"Start\n");
setup_wdt(WDT_ON | WDT_2S);
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It'll fail has he describes.
Or if he has a prescaler fuse setting somewhere.
On newer compilers it'll give 'WDT Postscale can only be set once', rather
than the error he currently has. |
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