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Will Guest
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Simple External Interrupt Handler |
Posted: Sat Oct 13, 2007 3:28 pm |
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I need to be able to run an ISR each time a line on a particular port changes. Sounds simple enough but I keep getting preprocessor errors when using any other port but B.
What am I missing? Below complies fine but doesn't seem to turn the
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#include <16F877A.h>
#FUSES NOWDT
#FUSES HS
#FUSES NOPUT
#FUSES NOPROTECT
#use delay(clock=20000000)
#include <stdlib.h>
#INT_RB
void alarm_ISR(void)
{
int8 tpb;
tpb = input_b();
if (tpb & 0x01)
{
output_high(PIN_A5);
}
else output_low(PIN_A5);
}
void main(void)
{
set_tris_b(0b00000111);
enable_interrupts(INT_RB);
enable_interrupts(GLOBAL);
} |
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PCM programmer
Joined: 06 Sep 2003 Posts: 21708
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Posted: Sat Oct 13, 2007 3:45 pm |
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Before you do anything else, add the NOLVP fuse. Without that fuse,
the PIC will lock-up if pin RB3 goes high.
Also, when you post code, enable the tickbox below the posting window
to disable HTML. Then you won't get lines like this:
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Ttelmah Guest
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Posted: Sat Oct 13, 2007 4:21 pm |
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Read the data sheet.
What pins does the RB interrupt respond to?.
Does this include bit 0 of the port, which you are testing?.....
Also, remember the need to have something to stop the main running off the end, and sending the processor to sleep.
Best Wishes |
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Will Guest
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Posted: Sat Oct 13, 2007 4:52 pm |
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I'll check again, but I was sure it responded to A5-A7 on port A, all of B.
The code above doesn't seem to respond either and I forgot my serial cable back on campus... |
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Ttelmah Guest
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Posted: Sun Oct 14, 2007 2:22 am |
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No, it responds to B4 to B7 _only_, you are testing B0....
Sction 12.10.3 in the data sheet.
On some chips, it responds to other bits, but not on the 877
Best Wishes |
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