26 Oct
1999
26 Oct
'99
1:53 p.m.
I would suspect that it was not intended to be tied
directly to a bus. One would normally have some robust
receiver that would invert the signal. In the days when
it was designed, the 0 to 2.5V TTL bus was just starting
out. Many had other voltage ranges and required some
conditioning. The simplest conditioning circuits usually
had an inverted signal out.
Dwight
Ah, not even close. TTL voltages on busses were old hat by then. The
intent was to NOT connect 8259 inputs directly on busses as they are MOS
devices and susceptable to damage. The expectation was at minimum an
inverter ahead of the input.
Also, many of the intel devices had interrupt pins that went active high.
That or maybe they ran out of room on the die for an inverter.
Allison