Can I use DH+ messaging to read output and to write input of PLC 5

[Thitiwut-Gelo]

Hello everyone. I have a question about Rockwell PLC communication.
Now I have a PLC5/30 and a Guardlogix 1756-L71S rack with 1756-DHRIO
In my PLC 5 there are Inputs & Outputs data for example I:041 - I:047 & O:041 - O:047 that I would like to read/write by DH+ message instruction with the setting in attached files.
Can I do that? or Should I change them to Binary(B) or Integer(N) data before?

 

[GaryS]

it may be possible to read I/O table in a PLC5 over the DH+ ( I have never done it directly ) and you can read the DHRIO directly over the DH+ I think you can actually have 3 devices read the DHRIO directly. I know you can read the data table over DH+ so you could just move the input table to another table and read it
but only 1 device can write to the DHRIO “ Master”
within the PLC5 again only one device (the master) or Local Processor can write to the output table but that problem is easily solve by writing to another data table in the processor and have the processor copy the value from the data table to the output table
just as a side note you can actually bridge a message between a DH device and a DH+ device
by the way i don't thing you message instruction is setup correctly

 

[Ken Moore]

I would move them to an 'N' register, then you can get them all with one read.

Set it up so that you are transferring extra registers, then in the future, if you need more data, just move it to a spare N register.

 

[Operaghost]

You can read and write to the PLC-5 I/O tables. Of course, if you are writing to the Output Data Table, any logic would overwrite the data. And if you are writing to an input table then the field devices would overwrite the data. But if all you want to do is read them, you should be good. The SLC 500 used to protect their I/O tables by default to prevent writing to them, but I believe they stopped doing that. You could manually turn off that protection, but it was protected by default. The PLC-5 never had this type of protection.

That said, I agree with the other posts to use a "B" or "N" file instead. It is less of a headache for the next person to troubleshoot. To me it looks like the MSG is configured properly. Perhaps GaryS can explain what is missing that I am not seeing. It appears you are exiting the DHRIO using Channel A and going to Node 53. Hopefully the O4 array is an integer (INT) type array.

OG

 

[alan_505]

I have directly read PLC5 output data tables into a ControLogix, but this was over ethernet so it should work over DH+, I was not able to write to the PLC5 Input data table but you should be able to read from the Input data table.