It's processor specific.

In the 17s:
"When an interrupt is reponded to, the GLINTD bit is automatically
set to disable any further interrupts,"

In 16C5X:
The OPTION reg does not disable global interrupts.
In fact, I can't find mention of global interrupts
in the Data Sheet book.  You can only turn Timer0
ints on and off.

In the 16C71X:
The GIE (Glable Interrupt Enable) bit is handled by the INTCON reg.
"When an interrupt is responded to, the GIE  bit is cleared to
disable any further interrupt, "

That's three somewhat different examples.
So in the 17s and some 16s it is done in Hardware.

Walt...

-----Original Message-----
From: Rob Zero [mailto:cyborg_0@IQUEST.NET]
Sent: Sunday, April 16, 2000 6:04 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: Simultaneous Interrupts


Software. Its done by writing to your option register.

Rob

----- Original Message -----
From: Kieran Miller <kiermill@DTN.NTL.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Sunday, April 16, 2000 7:03 AM
Subject: Re: Simultaneous Interrupts


> > This is why the global interupt is turned off when your interrupt
routine is
> > called, we don't want an endless loop.
>
> Is this done in software or hardware?
>
> Kieran
>