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TTL pulse on multiple channels

Hi!

I have to generate TTL pulses on multiple channels (at least 2) on LabPC+
DAQ boards in the same time or delayed.
Is there any possibility to have timed digital output on the DIO lines of
the 8255 and to set the pulse widths and delays using LabVIEW VIs? (LabPC
doesn't have o-board clock for DIO)
Or I should use the timer 8253 output for pulse generation but how can I
obtain pulses on more channels?
I appreciate any help,
Barna
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[This followup was posted to comp.lang.labview and a copy was sent to the
cited author.]

In article <38ea6b97@newsgroups.ni.com>, zajzon@ucla.edu says...
> Hi!
>
> I have to generate TTL pulses on multiple channels (at least 2) on LabPC+
> DAQ boards in the same time or delayed.
> Is there any possibility to have timed digital output on the DIO lines of
> the 8255 and to set the pulse widths and delays using LabVIEW VIs? (LabPC
> doesn't have o-board clock for DIO)
> Or I should use the timer 8253 output for pulse generation but how can I
> obtain pulses on more channels?
> I appreciate any help,
> Barna

It is possible...
I have done this for controlling a stepper motor driver with a PC-DIO-24
(also 8253) and controlling a group of mixing valves for
a toxicity
analyser (LabPC+, although PC-DIO24 would have done that part of the
job).

Buffered DIO is possible on these cards using handshaking, so the pulse
trains can be generated in software and then written out as a series of
updates.
My approach is to use an external flip-flop to drive the handshake lines
and control the rate at which this happens either with an oscillator or
using the LabPC+ clock output (which allows software control of the rate
the process happens).
With the PC-DIO24 in a '486 (ISTR DX2-66, maybe DX33) maximum reliable
speed was about 500Hz. I didn't investigate why it was so slow because
that was fast enough for the job.

Let me know if you are interested in this approach and I'll dig out the
circuit diagrams - there need to be a couple of transistors to drive the
LabPC+ lines adequately - and post them on a webpage somewhere.

Regards
Bernard Treves Brown
Whaley Bridge
UK.
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