29 Dec
1998
29 Dec
'98
1:49 p.m.
On Tue, 29 Dec 1998 ard(a)p850ug1.demon.co.uk wrote:
The PC? Well it has active high edge triggered
signals. I believe
(although I would have to check all the details) this saves one TTL chip
on the PC motherboard. A chip costing <$0.50 in _1 off_. And we've had
the IRQ sharing problem ever since....
If I understood, this could be summed up as:
When an interrupt happens, the interrupt line is pulled low by the
interrupting device. If it's edge triggered, the CPU can't tell how many
devices are causing the interrupt and only services the first one.
And are you saying that if they were level-triggered, I could have two
devices on IRQ 7? And is it easy to design a level-triggered equivalent
to the PC on paper? Are all PS/2 s level-triggered or only the MCA ones?
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Max Eskin | kurtkilgor(a)bigfoot.com | AOL: kurtkilgor