Morgan,
Check the data sheets. If I recall correctly, the
current operation is completed prior to the
interrupt routine being invoked.

But, if you are worried about such things, just
disable the global interrupt enable, use BSF to
set the individual interrupt bit you want,
enable the proper interrupt enable bit, and then
re-enable the global interrupt enable bit.

Fr. Tom McGahee

----- Original Message -----
From: Morgan Olsson <morgans.rt@TELIA.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Tuesday, October 19, 1999 8:01 AM
Subject: Software interrupt


How is software interrupt best generated on a PIC?

Most reliable seem to make a pheripheral generate an interrupt i.e by loading a
timer so it will
wrap immediately/very soon, or manipulate the RB0/INT pin so that generates an i
nterrupt.

But I need the timers for other tasks, and manipulating RB0/INT violates the int
errupt on change
functions.

An idea might be to directly set a pending flag (and of course the enable bit) f
or an else unused
interrupt source.
The manuals tell some of them are read/write :)

My worry about that is that the BSF command is a read-modify-write opeartion, an
d what will happen
if an interrupt flag get set by hardware between the read and write of the BSF.
 Probably that
interrupt flag will be overwrittten with the previous state!

Are there more reliable solutions?
Some experience?

Regards
/Morgan

Morgans Reglerteknik, Hdllekes, 277 35 KIVIK, SWEDEN
   tel +46(0)414-446620, fax -70331,   mrt@iname.com