Quick AB RIO Question

I have a SLC 5/04 with a 1747-SN module in it. Attached are a Flex I/O 1794-ASB and a 1791-16AC remote module. The 1794 is working fine and the SLC sees the data, but the data is not seen for the 1794. I checked all the wiring and switch settings and they seem to be okay. When looking at the 1747 configuration screen the correct number of input words and output words are there as to the attached modules.

My question is whether in the "G" data if a rack/group is selected that is not there, would this cause my symptoms? The 1794 is Rack 0, Group 0 and the 1791 is Rack 0, Group 4. The "G" data has Rack 0, Groups 0,2, & 4 all checked, all as 1/4 racks.

This was a project that was started by someone else years ago and I was asked to finish it. I know I have to make the change offline but will not be able to take processor down till tonight when we shutdown and just wanted to know if I am on the right track.

Thanks for your help,
Mark Snodgrass

With the G-File configuration you described, the 1747-SN is going to scan for three separate Adapters but one of them won't respond (Rack 00 Group 02).

That will cause some delay, but not a malfunction.

If you can, provide details on the 1794 FLEX modules that are attached to the 1794-ASB adapter, as well as the full DIP switch settings of both the 1794-ASB and the 1791 Block adapter. Also be sure to determine and post which Series letter the 1794-ASB adapter is (Series E is the most common modern one).

Sometimes it takes a second or third set of eyes to see things we overlook when dealing with complex configuration settings.

Ken,

The 1794-ASb is series E. The modules connected to it are a 1794-IA16, a 1794-OA16, and a 1794-IA16.

The dipswitch settings for the 1794-ASB are SW1-->All on, SW2--> 1 on, 2 on, 3 off, 4,5,6,7 on, 8 off.

The dip switch settings for the 1791 are SW1--> 1 off, 2 on , 3,4,5,6,7,8 off and SW2--> 1&2 on, 3,4,5,6 off, 7 on, 8 off

Thanks

I agree that the DIP switch settings look correct.

The 1794-ASB adapter is set for "Compact" addressing. With 16-point modules, this means that you need to alternate Input and Output modules. Those three modules you described add up to just 1/4 Rack.

I would still remove the checkbox for Rack 00 Group 02 (1/4 Rack) in the G-file configuration.

You might also change the Last Rack switch (SW2-6) on the 1791-16AC Block. Because it's the highest numbered partial-rack addressed device for Rack 00, it is in fact the "last rack".

Triple-check the wiring:

1747-SN Blue on Top, Clear on Bottom
1794-ASB Blue on Left, Clear on Right
1791-16AC Blue on Top, Clear on Bottom

And of course make sure you have 82 ohm terminating resistors at each end of the link and nowhere else.

Ken,

Good catch on the dipswitch, I have had that bite me in the butt before. Changed the setting and cycled power on the 1791 only (we were running this morning when I read your message). Still not getting the data table to update, I will try tonight to uncheck group 2 and cycle power to the whole system to see if that remedies it.

thanks

No luck so far. Tried the items in my previous post with no luck.

Another question about the setup that I am unfamiliar with. In the scanner configuration is scanned inputs and outputs, which the manual says is the number of words the processor scans from the 1747-SN. Is this sequential starting at word 0, (ie. If set to 4, it scans words 0,1,2,3) or does it skip words not assigned in the G data ( it scans 0,1,4,5 if group 2 is not assigned)?

Thanks

You might have found the problem; is the I/O size of the 1747-SN set for 4 words Input ?

The default value for the Scanned Input Words and Scanned Output Words is 32. Unless you have a packed chassis with lots of analog and speciality modules, it's typically left at 32 words.

The data is arranged sequentially, not "compacted". Data from Logical Rack 00 will always be in words 0-7, from Logical Rack 01 in words 8-15, and so on.

Let's say the 1747-SN is in Slot 4. The data from your system will be mapped as:

I:4.0 1794-IA16 in FLEX Slot 0
I:4.1 1794-IA16 in FLEX Slot 2
I:4.2 Available for Rack 00 Group 2
I:4.3 Available for Rack 00 Group 3
I:4.4 1791-16AC
I:4.5 Unused
I:4.6 Available for Rack 00 Group 6
I:4.7 Available for Rack 00 Group 7

O:4.0 1794-OA16 in FLEX Slot 1
O:4.1 Unused
O:4.2 Available for Rack 00 Group 2
O:4.3 Available for Rack 00 Group 3
O:4.4 Available for Rack 00 Group 4
O:4.5 Available for Rack 00 Group 5
O:4.6 Available for Rack 00 Group 6
O:4.7 Available for Rack 00 Group 7

You could technically get by with the G-file set for 5 Input Words and 1 Output Word, but I would set it for a minimum of 8 Input, 8 Output just to emphasize that you're scanning Rack 00 only.

I have actually been dreaming about this problem, I was so obsessed with it. Knowing that they are sequential, that must be the issue. I wont be able to try and correct it until tomorrow afternoon, but I will let you know if it works.

Thanks

Thanks Ken for all your help. The scanned input and output words was the issue. I have not previously seen the configuration changed from the default, so this was a new one to me. Now I think I know more about the 1747 scanner then I want to.

Mark Snodgrass