SNAP Multi-Channel I/O Confusion - old forum post


Joined on 06-23-2007
Posts 6
SNAP Multi-Channel I/O Confusion

Just started working with the SNAP Multi-Channel I/O.

One of the first things that jumps out at me is that in the point configuration the module channels are identified 0-3 (4-channels). On the module itself the wiring diagram identifies the channels 0-3. However, the red lights that show the I/O status are identified 1-4. Shouldn’t we stick with the 0-3 pattern?


05-30-2008, 1:40 AM


Joined on 12-01-2003
Optomation Systems, Madrid, Spain
Posts 153
Re: SNAP Multi-Channel I/O Confusion

Kind of reminds me of the question, “When did the 21st Century Start”!

You are quite right, the LEDS on 4 channel module have always been a bit “Querky". The origin of the problem was probably Opto22 Quad Pak I/O which didn’t use any software from Opto22 so there was no confusion. You were also lucky to miss the fun of working with SNAP-B3000, which achieved the admirable compatibility with MisticI/O by considering the modules on a single 16 module rack as being 4 different virtual racks each with 0-7 modules. Normality briefly returned with the B3000-ENET as before the introduction of HD modules all points were nearly understandable by using 0-63 referencing on the rack. As the LEDs always indicated 1-4, it was almost obvious that the point number did not coincide with the LED.

After a couple of painful years of mixing HD referencing (Module 0-15 and Channel 0-31) with standard 4 channel I/O referencing 0-63 points, PACControl 8.x has now standardized on module-channel number, which now makes it much easier and cleaner from a software point of view, but which can lead to some confusion if you just look at the LEDS. Sometimes improving technology is like that.

Possible solutions include only using HD modules (No Leds!) or you putting a cross reference chart in the panel where the PAC is installed indicating Module, Channel, LED, Tag and Description for each point. The best solution by far would be for Opto22 to include the LED indicator number in the “Configure I/O Points Dialog” dialog and Debug “View I/O Unit” window in PAC Control.

But as the Chinese good luck proverb says “May you never achieve what you most wish for”. The difficulty with changing the red and white plastic indicators is the installed base out there. Imagine the fun mixing modules with 1-4 indicators and 0-3 indicators. What percentage of the 85 million Opto22 modules out there are SNAP 4 channel digitals?

Maybe we should just start a Facebook user group “Opto 22 SNAP LEDs [0-3]: Support The Change”, Perhaps with more than 5,000 members we could force the issue.


P.S. The answers 1st Jan 2001. A century contains 100 years and not 99, so, the end of the first hundred years happened at the end of the year 100, and not at the end of year 99!