In order to reset the count on a z-index input with your M-series board, you'll need to configure this as an encoder position measurement. Since you only have an A channel, you won't be able to configure as a quadrature encoder. What you
*can* do is configure as a "Two Pulse Encoder" which counts up for each edge at the channel A input and counts down
for each edge at the channel B input. Just wire one of those inputs direct to DGND to eliminate any possibility of edges.
You'll further need to configure and enable the z-index reload feature for encoders. Here's the tricky part - you are required
to define the A,B state in which a high state of Z will reload the z-index value. The problem is that the z-index signal may
not have the timing characteristics you'd like. I don't know if your app is particularly sensitive to this issue, but I'll lay it
out:
Let's suppose you set z-index reload phase to be A-Low, B-Low with one of them hardwired to DGND (guaranteed Low).
Here are 3 things that could happen:
1. A is low throughout the Z-index signal's high time. Your reload works just as you want. (It will probably also work as
you want for other situations where A is low during exactly one segment of the Z-index signal's high time. A could be
high during 0,1,or 2 distinct segments of that time. The key thing is that once A is low, it can't transition to high and back
to low in order to work as you probably want.)
2. A is high throughout the Z-index signal's high time. No reload takes place due to the wrong A,B phase.
3. A has 2 or more distinct segments of low time during the Z-index signal's high time. 2 or more reloads will take place,
causing the intervening edge counts to be ignored.
-Kevin P
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