clear pending interrupt of external-int0

hamedhamedi · Joined: 12 Feb 2012 Posts: 70

Hi
i want to disable int0 in some section of my code and enable it again in other section of my code,but a problem occur .
when i enable int0 again my code,the pending interrupts that occur during disabled it0, led to run routine of int0 once.
so i want to clear pending interrupts before i enable it again.
i know from datasheet that writing logic one to flag of an interrupt clear it,but refer to some website like this below,confuse me!

http://www.avrfreaks.net/forum/clearing-pending-interrupts

any idea for clear pending interrupt in bascom avr?

Thanks

(BASCOM-AVR version : 2.0.7.7 )

dabatek · Joined: 31 Jul 2013 Posts: 27 Location: Serbia

GIFR=64

hamedhamedi · Joined: 12 Feb 2012 Posts: 70

thanks dabatek
how it work?

dabatek · Joined: 31 Jul 2013 Posts: 27 Location: Serbia

From Data sheet:

General Interrupt Flag
Register – GIFR[/b]

• Bit 6 – INTF0: External Interrupt Flag 0
When an edge or logic change on the INT0 pin triggers an interrupt request, INTF0 becomes set
(one). If the I-bit in SREG and the INT0 bit in GICR are set (one), the MCU will jump to the corresponding
interrupt vector. The flag is cleared when the interrupt routine is executed.
Alternatively, the flag can be cleared by writing a logical one to it. This flag is always cleared
when INT0 is configured as a level interrupt.

Have a nice day, Hamed Smile

AdrianJ · Joined: 16 Jan 2006 Posts: 2477 Location: Queensland

@databek
Perhaps it would have been more obvious if you had written

set GIFR.INTF0

rather than

GIFR = 64

I know its ( almost ) the same thing, since clearing bits in the GIFR does nothing, but maybe other people dont.

hamedhamedi · Joined: 12 Feb 2012 Posts: 70

in the website i post its link,there are different ways of set a bit,and there are very description for its different type. as different way AdrinJ and dabatek say.
some other way is shifting GIFR register. i want to know what of them should work true in bascom avr?
thanks

AdrianJ · Joined: 16 Jan 2006 Posts: 2477 Location: Queensland

databek is correct, its better to write the entire register with just the one bit set that you want to clear, rather than use the SET instruction, which does a read-modify-write. This only applies to these really odd registers like GIFR, which use setting a bit to clear it !

albertsm · Joined: 09 Apr 2004 Posts: 5119 Location: Holland

SET does not read/write modify on FLAG registers.
Set uses SBI when possible, and when the register is marked in the [FLAG] section and is an extended register, it will not do a read but just a write.
So it is safe to use SET