HANDLING THE INTERRUPT. - Electronic Circuits Projects Diagrams Free

alamy · 21st March 2005, 08:54 AM

I have two interrupt, the first one is USART interrupt using hardware approach and another one is external interrupt at RBO interrupt, this one for USART software routine.

My software USART only receives the data while hardware USART do receive and transmit the data.

The case is, the interrupt occurred to my software USART (external interrupt, RBO) and than, it will process the data received, but before the task finish, the second interrupt which is hardware USART occurred, my question is, how PIC handle this thing?

I want my PIC finished the first task (software USART) and then process for the second one. So do if the interrupt hardware USART occurred first. The idea is …I want my PIC finish the task that come first and then continue for the second one…

Please advice…thanks in advance.

Pommie · 22nd March 2005, 06:39 AM

The interrupt will behave as you want it to. Interrupts are automatically disabled at the start of the interrupt and stay disabled until the retfie.

You can enable them while still in the interrupt by setting the Global enable bit, but re-entrant interrupts are not the easiest thing to get working.

I think that if I was doing this then I would only have the port b interupt and handle the hardware usart in the main loop.

HTH

Mike.

alamy · 23rd March 2005, 01:35 PM

thanks ...but i still can't get the idea since i'll have two interrupt at the same time...

My confusion is on...when the first interrupt happen and suddenly the second interrupt coming...how the pic handle this interrupt...respond to the second one.?.

how should i do, if i want my PIC continue with first interrupt(completed the task) while at the same time respond to the second interrupt...

your comment are highly appreciated.

thganks

**Nigel Goodwin** · 23rd March 2005, 01:55 PM

As Pommie already said, as soon as an interrupt is called any further interrupts are disabled. At the end of your interrupt service routine you should re-enable interrupts again - if there has been an interrupt whilst they were disabled, it will be triggered then.

But, like Pommie, I fail to see why you are wanting to try and use interrupts for both?.

**Jay.slovak** · 23rd March 2005, 01:56 PM

Quote:

Originally Posted by alamy

thanks ...but i still can't get the idea since i'll have two interrupt at the same time...

My confusion is on...when the first interrupt happen and suddenly the second interrupt coming...how the pic handle this interrupt...respond to the second one.?.

how should i do, if i want my PIC continue with first interrupt(completed the task) while at the same time respond to the second interrupt...

your comment are highly appreciated.

thganks

Ok, here's the point: If PIC is in ISR, and gets another interrupt request, the PIC keeps working on first interrupt. When it's done (RETFIE) it will re-enable interrupts and the second interrupt will take place. that's it...

alamy · 25th March 2005, 09:09 AM

ok ..thanks...i get it..

BF9000 · 26th March 2005, 03:37 PM

As soon as an interrupt occurs, the GIE (global interrupt enable) bit is cleared and the ISR is entered. This disables any further interrupts. However, interrupts flags may still be set during the ISR. As soon as the RETFIE instruction is executed, the GIE bit is automatically set. At this point, the ISR will be executed again if any unmasked interrupt flags were set. Remeber to clear the appropriate interrupt flag at the beginning of your ISR.

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21st March 2005, 08:54 AM	(permalink)
alamy	HANDLING THE INTERRUPT. I have two interrupt, the first one is USART interrupt using hardware approach and another one is external interrupt at RBO interrupt, this one for USART software routine. My software USART only receives the data while hardware USART do receive and transmit the data. The case is, the interrupt occurred to my software USART (external interrupt, RBO) and than, it will process the data received, but before the task finish, the second interrupt which is hardware USART occurred, my question is, how PIC handle this thing? I want my PIC finished the first task (software USART) and then process for the second one. So do if the interrupt hardware USART occurred first. The idea is …I want my PIC finish the task that come first and then continue for the second one… Please advice…thanks in advance.

22nd March 2005, 06:39 AM	(permalink)
Pommie	The interrupt will behave as you want it to. Interrupts are automatically disabled at the start of the interrupt and stay disabled until the retfie. You can enable them while still in the interrupt by setting the Global enable bit, but re-entrant interrupts are not the easiest thing to get working. I think that if I was doing this then I would only have the port b interupt and handle the hardware usart in the main loop. HTH Mike.

23rd March 2005, 01:35 PM	(permalink)
alamy	thanks ...but i still can't get the idea since i'll have two interrupt at the same time... My confusion is on...when the first interrupt happen and suddenly the second interrupt coming...how the pic handle this interrupt...respond to the second one.?. how should i do, if i want my PIC continue with first interrupt(completed the task) while at the same time respond to the second interrupt... your comment are highly appreciated. thganks

23rd March 2005, 01:55 PM	(permalink)
Nigel Goodwin	As Pommie already said, as soon as an interrupt is called any further interrupts are disabled. At the end of your interrupt service routine you should re-enable interrupts again - if there has been an interrupt whilst they were disabled, it will be triggered then. But, like Pommie, I fail to see why you are wanting to try and use interrupts for both?. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

25th March 2005, 09:09 AM	(permalink)
alamy	ok ..thanks...i get it..

26th March 2005, 03:37 PM	(permalink)
BF9000	ISR As soon as an interrupt occurs, the GIE (global interrupt enable) bit is cleared and the ISR is entered. This disables any further interrupts. However, interrupts flags may still be set during the ISR. As soon as the RETFIE instruction is executed, the GIE bit is automatically set. At this point, the ISR will be executed again if any unmasked interrupt flags were set. Remeber to clear the appropriate interrupt flag at the beginning of your ISR.