1756-DHRIO to 1794-ASB. Adding IE8 Card

Chris90

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Jun 2020
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Hello all. I have a job to add a 1794-IE8 Card in slot 5 on an existing Flex IO Rack which uses a 1794-ASB communications module, which communicates to a 1756-DHRIO control logix card. The existing rack only has digital cards in it so far which is why there is no BTR/BTW instructions to copy from. I have zero experience with this kind of communications however i have used MSG instructions in the past.

In terms of retrieving the data from the 1794-IE8 card, i've read that you have to use BTR/BTW instructions. With control logix this is all now handled in the MSG instruction. I've seen an example bit of code which only used a BTR MSG instruction but no BTW?

I have attached screenshots of the current setup. If i need a BTW in there on first pass or anything do you have an example piece of code or point me in the right direction as to how to set this up? the job is only adding 1 flow meter to channel 0 of the new card (4-20ma).

Unfortunately this is a suck it and see it type of job where i'm unable to test in the office prior to site attendance so i'd like to have some confidence that i'm at least heading in the right direction before attending site

In terms of dip switch settings, is there anything i may have to change on the ASB module when adding an analogue card?

Many thanks in advance. I've only been programming for 10 years now so i've been brought up on mainly ethernet!

Screen shot 1.jpg
 
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Welcome to the forum, Chris...cracker of a question to start...!

I do have a CLX PLC setup like this, but not done by ourselves.

Yes, you will need a BTW message to the IE8 module to setup the configuration.
Send one integer word to the IE8 in the format in the attached document.
e.g. all channels 4-20mA 0000000011111111

You may also have a tag
LMCC3:I.InputGroupsValid, which if you look at the individual bits 0-5, there should be a 1 for a digital card and a 0 for an analog card.

My BTRs for 1794-IE8 have a length of 9 elements, which I recall was the same for PLC5 config too....

Does any of the above make sense? I hope so....
I need to go off and get back to work.
 
Yes that makes sense thank you! i'll change the elements to 9, i can see this now in the manual

As for the data itself, will this be presented in the typical raw format of 0-30840? which i can then map to a scaling block in my CLX.
 
Hi John Hope you are well.

I've finally got the slot to do the job today.

Performed the download but i am seeing errors on the messaging block (16#00d0) Map instance undefined; or block transfer timeout.

All dip switch settings on S1 & S2 are set to ON (1-8) which remain unchanged. I'm assuming 3/4 rack size is still correct for the following layout:

Slot 0 = 16 Channel Digital Input Card (1794-IB16)
Slot 1 = 16 Channel Digital Input Card (1794-IB16)
Slot 2 = 16 Channel Digital Input Card (1794-IB16)
Slot 3 = 8 Channel Digital Output Card (1794-OW8)
Slot 4 = 8 Channel Digital Output Card (1794-OW8)
Slot 5 = New 8 Channel Analog Input Card (1794-IE8)

Also got each slot as its own group (new card slot 05 = group 5=

I have read online that there could be issues on power cycle that you should have the analog card powered up whilst power cycling the rack as there could be timing issues? trying that tomorrow

Also the Revision of the 1794-ASB module is Rev D

Any further help would be welcome!

Ladder.png BTR.png BTW.png
 
I have a few IE8’s in a similar setup running. I didn’t add the analog module to the IO tree. It just messaging to it’s location. The read message is 8 elements. Try this in the communication tab of the MSG:

Path will just be your DHRIO name. In your case it looks like LMCC3_FlexIO. You can browse and select your module or type it in.

Module address will be RIO, Channel B, Rack 0, Group 5, Slot 0

Cache Connections on is fine unless you have lots of other comms happening.

The way the message is written to retrigger immediately looks like you want the data quickly. For the analog levels I’m reading, I read once a second then the data is filtered for even slower response. I have a large network with 50 ASB modules between both channels so I kept the messaging events low. I write the configuration data to the modules about every minute in case a rack gets power cycled. That’s quick enough for what we’re doing.

Edit - I didn’t notice your configuration tab in the pic previously. That looks correct.
For 4-20 mA on all channels and all enabled I'm writing 1111111100000000 or -256 in decimal.
 
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Thank you for the reply, really appreciate it!

With regards to 9 elements, I looked in the manual and the 9th element are status bits for the 8 channels? Example [8].0 being the under range bit for channel 0. I will try 8 elements though as a test.

Going to try inhibiting the messaging then performing a power cycle to the asb rack with the analogue module still powered up (apparently there can be issues if the asb powers up before the analogue module) then initiate a single write message and then start the reads every second and see how I get on

Looks like the rack and group settings are correct so I don’t need to perform another download at least. This site has one PLC that covers the full
Site with different systems so getting a shutdown is a nightmare!

Many thanks again
 
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Ah....the old "bent pin" scenario......Happens to the best of us...

I have just spent the last couple of hours battling with a PLC5-80E that had lost its program. Finding the right cables to use, USB to serial, getting the COM port to work, then downloading the program to the PLC at warp factor -10, then downloading the latest version on ethernet eventually as my old laptop had an old copy.....gotta love this old technology!
 

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