Hi,

 Could anyone please explain how the PIC16F84 will behave in the
following situation ?
 (After reading the datasheets it still isn't clear...)

Global interrupts      = enabled
Interrupt on RB0/INT   = enabled
Interrupt on TMR0      = enabled

Situation (example):

Timer generates an interrupt.
ISR checks for cause and determines it was TMR0.
Services interrupt for TMR0 cause.
Clear TMR0 flag
RETFIE

Sometime during the ISR (after checking cause), RB0/INT signals an
interrupt. What happens next ?
(I expect in my application to have at most 2 interrupt signals on)

Questions:
1) should I disable GIE in ISR or leave it on?
2) if I leave it on, if an interrupt occurs during ISR, it will call
ISR again from start ?
3) i think this should be yes: at top of ISR I should disable GIE, save
context, clear cause flag, reenable GIE  ?
4) should the cause flag be cleared at the beginning or end of ISR?
(related to #3 above)
5) if I disable GIE, after servicing the entire ISR, after RETFIE, a
new interrupt will be generated by the active RB0/INT signal?

Thank you.




=====
ing. Andrei Boros
Centrul pt. Tehnologia Informatiei
Societatea Romana de Radiodifuziune

__________________________________________________
Do You Yahoo!?
Yahoo! Auctions - buy the things you want at great prices
http://auctions.yahoo.com/

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu