Folks,

Hopefully we haven't just recently covered this topic but here goes.

I'm having problems using the timer 1 counter on a '73. When I drive the
input from a nice square wave everything works fine. However I really need
to count pulses via an I/O module (like a IAC or IDC). These devices have
an open collector output which produces a slow rise time pulse edge when
the transistor turns off. Normally this isn't a problem if you run this
signal into a schmitt trigger. Fortunately the timer 1's counter circuitry
includes a schmitt trigger.

Here's the problem, I send my PIC ten pulses at 1 pulse/sec through the IAC
module and count about 400 pulses. On the scope, the counter signal looks fine
with a somewhat nice rise time (definately not oscillating or noisy).

So my question are,
        does the '73 timer1 counter have schmitt triggers on the input?

        is there a minimum rise time requirement for the counter?
                (not that it needs one if the schmitt trigger actually works)



Just counting pulses like mad,
craig