SL9696-VRE Modbus Communication

[Jacob Brown]

I have a SL9696-VRE temperature controller that I need to communicate to via Modbus ASCII (RS-485). I have a PLC with a Point IO 1734-AENT and a 1734-485ASC attached to the Point IO module. There are transmit and receive wires going from the ASCII Module to the Temperature controller. I know that communication to the ASCII module is good, but trying to send an ASCII string to the temperature controller yields no change on the temperature controller. At this point, it might be my ASCII string. It begins with a ':' character, the address, function, data, empty bit for error, then my ending CR-LF characters. Any advice? Thanks!

 

[danatomega]

I couldn't find any information about the formatting of the string but I am still looking ...

However, in the manual:
https://www.jlab.org/accel/inj_group/vacuum/SoloTemp/solo%20manual.pdf

it says:

Note: Make sure the On-Line Configuration parameter (​

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Cosh, P3-12) is set to ON.
The parameters in the SOLO controllers can be changed by the MODBUS network​

master only when the parameter is ON. (It is OFF as the factory default.)

 

[OpZed]

Head on over to:
http://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf
Then start at Section 2.5.2.1 (Page 17).

It also might be useful to watch the transactions of a known good master before trying to roll your own.
http://www.modbustools.com/modbus_poll.html

 

[Jacob Brown]

@danatomega: I have the COSH parameter set to ON. Here is my string:
start ':'
address '$02'
function '$10'
starting address high '$10'
starting address low '$01'
no. of registers high '$00'
no. of registers low '$01'
byte count '$04'
data high '1'
data low '8'
data high '0'
data low '0'
error check '$00'
end delemeter CR '$r'
end delemeter LF '$l'
The starting address, no. of registers, byte count and data are all in the data part of the modbus message.

 

[cjh]

I concur with OpZed. You should download Modbus Poll and turn on the "Communication Traffic" window to see how the string should be formatted.

Just a quick glance to me indicates that you are sending the wrong LRC value (what you call "Error Check"). It should not be 0.

 

[Jacob Brown]

Okay. For my error check, I get '$0F'. I tried it and it still doesn't work, I will give Modbus Poll a try.

 

[Jacob Brown]

How does this look? Which transmit string should I go by, the first one that transmits or the second one? Before each receive, there seems to be two transmits.

 

[OpZed]

In Modbus Poll you've got two devices defined. Click and drag that window over a bit and you'll probably see another one underneath. In your capture there's a request to Node 1 which is timing out. Then a request to Node 2 which is responding with an Exception code. What register are you trying to write to?

 

[Jacob Brown]

I am trying to write to register 44098 (or 4098 according to Modbus Poll).

 

[Jacob Brown]

Never mind guys, I figured it out. Thank you for all of your help, Modbus Poll turned out to be really helpful, and automation direct even said to use it, so if anybody sees this in the future, USE MODBUS POLL!! I am able to figure out my own LRC's and strings. Thank you all again for your help!