Multiple Interrupts on PIC16F876

[Joerg Hahn]

Hello everyone,

I'am still working on a project, where I have to use 2 different interrupts (int_ext and int_timer2) to switch between 2 different synchronise clockings (internal clock via timer2 and external clock via int_ext).
It is possible to work with 1 or 2 different ISR's on a PIC16F876 with 2 different interrupt sources (switchable from control-software on PC)?
#int_global is not working and only #int_ext is not enough.

Have everyone an idea?
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516001

[R.J.Hamlett]

:=Hello everyone,
:=
:=I'am still working on a project, where I have to use 2 different interrupts (int_ext and int_timer2) to switch between 2 different synchronise clockings (internal clock via timer2 and external clock via int_ext).
:=It is possible to work with 1 or 2 different ISR's on a PIC16F876 with 2 different interrupt sources (switchable from control-software on PC)?
:=#int_global is not working and only #int_ext is not enough.
:=
:=Have everyone an idea?
This appears to be relatively simple.
You have to write two interrupt handlers, each of which increments the required counters, and sets any flags needed to keep the main code synchronised. Each routine should be written to use the same storage locations in global storage for these values.
Then the main code should enable_interrupts(global), setup the required polarity for the external interrupt, and polarity/prescaler for the timer2 interrupt. Then to switch between the routines, you should disable the current routine, clear the interrupt flag for the second routine, then enable this. So a routine like:

#define I_EXT 0
#define I_TIMER2 1
#bit T2IF=0xC,1
#bit EXIF=0x8B,1

switch_to_interrupt(int int_reqd) {
//Ensure neither interrupt is enabled
disable_interrupts(INT_EXT);
disable_interrupts(INT_TIMER2);
if(int_reqd==I_EXT) {
//prevent immediate interrupt for past rollovers
EXIF=0;
enable_interrupts(INT_EXT);
}
else {
T2IF=0;
enable_interrupts(INT_TIMER2);
}
}

Then in main (or anywhere else), you can just 'switch_to_interrupt(I_EXT)', and this will start executing the INT_EXT handler, but leave the INT_TIMER2 handler uncalled.

Best Wishes
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516004

[Joerg Hahn]

:=:=Hello everyone,
:=:=
:=:=I'am still working on a project, where I have to use 2 different interrupts (int_ext and int_timer2) to switch between 2 different synchronise clockings (internal clock via timer2 and external clock via int_ext).
:=:=It is possible to work with 1 or 2 different ISR's on a PIC16F876 with 2 different interrupt sources (switchable from control-software on PC)?
:=:=#int_global is not working and only #int_ext is not enough.
:=:=
:=:=Have everyone an idea?
:=This appears to be relatively simple.
:=You have to write two interrupt handlers, each of which increments the required counters, and sets any flags needed to keep the main code synchronised. Each routine should be written to use the same storage locations in global storage for these values.
:=Then the main code should enable_interrupts(global), setup the required polarity for the external interrupt, and polarity/prescaler for the timer2 interrupt. Then to switch between the routines, you should disable the current routine, clear the interrupt flag for the second routine, then enable this. So a routine like:
:=
:=#define I_EXT 0
:=#define I_TIMER2 1
:=#bit T2IF=0xC,1
:=#bit EXIF=0x8B,1
:=
:=switch_to_interrupt(int int_reqd) {
:= //Ensure neither interrupt is enabled
:= disable_interrupts(INT_EXT);
:= disable_interrupts(INT_TIMER2);
:= if(int_reqd==I_EXT) {
:= //prevent immediate interrupt for past rollovers
:= EXIF=0;
:= enable_interrupts(INT_EXT);
:= }
:= else {
:= T2IF=0;
:= enable_interrupts(INT_TIMER2);
:= }
:=}
:=
:=Then in main (or anywhere else), you can just 'switch_to_interrupt(I_EXT)', and this will start executing the INT_EXT handler, but leave the INT_TIMER2 handler uncalled.
:=
:=Best Wishes


Thank you. It's working now working

Best wishes
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516064