The 5000-character limit prevents me from answering your questions in full. In precis:
Why gate inputs? Because on the TIO-10, you could tie the gate input to both the gate and the source of a counter. This allowed enabling (opening) the gate on the rising edge, counting and closing the gate with the falling edge, counting one event. Because the original project used this, and the engineer (now manager) who evaluated recreating the original project stipulated no changes to the software, I was told that I must tie to the gates PFI's.
experimental results from yesterday:
a) unless we missed something very important, you can't connect a gate line to the source input of the same counter, at least not in Traditional NI-DAQ(legacy)
b) neither were we able to connect a gate PFI to counter X to the input of its paired counter. (The documentation is so confusing on this point that it looks like it is saying that we can connect the gate of counter(0) to the source of counter(1), not PFI_38 to the input of counter(1)!)
c) I needed to short (jumper) PFI_38 to PFI_39 so that the signal being provided to PFI_38 could get through PFI_39 to the counter source for (internal)counter(0), allowing us to prove that the 6602 board was, indeed, still functional, and that a switch closure on the input to my interface board could, indeed, cause an event to be counted by the 6602 board. Because of the relatively high impedance of the PFI inputs, the driving CMOS output signal from the debouncer chips was able to drive both input lines, and yes, we were able to count, so I could redesign my interface boards, get new ones made, and only lose a week on this project.
The manual is very confusing on the matter of what can be connected to what. With the confusions between source(0) as a PFI line and source(0) as an internal counter input, it was easy to interpret the 'other counter gate' connection as tying two inputs together with no driving signal. The addition of a single quote (prime) to the actual internal counter inputs would demystify the manual by half. A clearer statement (perhaps an additional sentence in section 3, Device Description third paragraph stating "Likewise, for 660x series devices, any gate PFI (PFI_38, PFI_35, etc) can be selected as gate inputs to the counters.") would be desirable.
There is a whole other issue of Traditional NI-DAQ (legacy) vs. NI-DAQmx, and what they enable to be programmed on the 6602, but the 5000-char limit precludes raising it properly.
At this point, the boards have been recast, inputs to source PFI's, gate PFI's brought out to tie high or low, and new boards are being made. We're only losing a week.
