1756 dhrio

Darkzadow

Member
Join Date
Nov 2011
Location
Phily
Posts
94
Hi. I know this question has appeared several times in the past but I can't seem to get messaging to work.

I have a pc with ethernet to PLC1 and a dh+ connection to PLC2. I can program and connect to PLC2 just fine but when I try MSG from either PLC they do not connect. I am trying to use CIP message type.

Both PLCs are CLX 5000 and both have DHRIO with both channels in DH. The communication path is local so I shouldn't need a routing table but I added one anyways as PLC1 has other DH connection on channel B. when i try a message from either PLC I get a connection failure Error code 16#0001 Extended Error code 16#0000_0204 that one person on the forums had before, but I tried the path with both octal and decimal values to no luck. I was thinking someone could see any obvious mistake I have.

Situation

PLC1:
CLX 5000
DHRIO slot 4
node channel A=10
node Channel B=11
Channel A local with only PLC2 on it DH+
Channel B local with multiple PLC-5s DH+
Routing table:
Channel A- DH+ [Link10]
|--DH+ Bridge -Node 31
|-------Bridge [link undefined]
Channel B- DH+ [Link11]

Local DH+ connection both on CH-A

PLC2:
CLX 5000
DHRIO slot 1
node channel A=31
node Channel B=32
Channel A local with only PLC1 on it DH+
Channel B empty
Routing table:
Channel A- DH+ [Link10]
|--DH+ Bridge -Node 10
|-------Bridge [link undefined]
Channel B- DH+ [Link undefined]

From PLC2 i try CIP data read with path 1,1,2,12,1,0

With or without the card in the IO configuration I get com error mentioned above.

I am a bit lost because I can program to PLC2 over the dh connection but msg does not work. Any ideas on why msg does not work?

I was thinking of resorting to PLC-5 data mapping cause I know PLC1 uses it on CH-B but got same error on couple tries that way too.
Any help would be amazing.
 
Last edited:
Since you are using only DH+, don't put the 1756-DHRIO modules in the I/O tree.

Try the CIP path from PLC2 to PLC1 of "1,1,2,8,1,0"

DH+ addresses are expressed in Octal on the modules and in RSLinx Classic, but in the Path field of the MSG instruction you need to either express them in Decimal or note them as "8#10" for Node 10 Octal = 8 Decimal.
 
Ok i had the conversion backwards. I will try that and feel silly for not trying the conversion both ways. I will let you know how that works. Thank you
 
One way I drive my colleagues nuts: when we work on DH+ or PLC-2/3/5 systems, I always pronounce Octal or Hexadecimal numbers by their digits and add a leading zero.

So "08" is "Zero Eight" and "12" is "One Two", not "Twelve".

This way every value has two digits and because it's a little discordant to hear, it reinforces that we are talking about old-fashioned addressing.
 
OK That did work i feel slightly stupid I didn't convert the other way. Thank you guys, and I will use that method of talking about it cause my coworkers thought everything was in decimal.
 
Definitely don't feel bad; it's a very common issue.

In fact, look at the example on page 7-1 of the 1756-UM014 user manual for the 1756-DHRIO.

The target 1756-DHRIO has the DH+ address called out in the block diagram as "030", clearly in Octal.

But the screenshot for the CIP Path shows the target address as "30". It should either be "24" in Decimal, or "8#030" to show that it's in Octal.

The use of "8#" or "16#" prefixes to designate Octal or Hexadecimal is described on page 3-16 of the User Manual.
 

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