1756 MVI configuration

[SCAN.PLC]

Hi ,

I am using Prosoft communication module (MVI 56-MCM)MODULE.
I configured the port 1 for Modbus slave with RTU protocol.
Communication link is on RS232C cable connected to DCS via PHONIX CONTACT (serial to fibre optic convertor).
when connected to DCS link my port 1 LED is showing continous GREEEN.BUT DCs serail to fibre converter Tx and Rx not blinking green .they are Tx is blinking green and Rx is blinking Amber.
If data transmission is happening then as per manual it shold blink rapidily.
Onaly 2 cables are used in this transmission. transmit , recieve and ground.
RTS & CTS are jumpered.

Also where i should configure the MODULE internal write data block (DCS will read from this addresses) start address.

Also i can see the diffrent offsets for Bits and Integers to be written to internal data block.
How in program that i should tell the module that this is data is bit andthis is Integer.


hope some one can clarify me on this.

 

[Ken Roach]

In Modbus protocol, "Bits" and "Integers" are referred to as "Coils" and "Holding Registers". They are handled by specific Modbus function codes.

Has your DCS programmer defined exactly which Modbus addresses or Modbus function codes he requires you to respond to ?

For troubleshooting, I use the very handy diagnostic port on the MVI56-MCM. That will show you if data request commands are coming through from the DCS, and how they might be responded to.

You could also hook up a terminal emulator or serial analyzer to the fiber converter to detect and "See" the data requests from the DCS.

For configuration questions, you're going to have to post specifics about the Modbus addressing and maybe post what you already have configured for the MCM module.

 

[bwheat]

Like Ken said connect to the MVI using the serial port. You can use hyperterminal. This will give you an idea what the module is being instructed to do. Talk to the Prosoft tech support group. They have a new manual out on the 1756 module and it is much better than the old one. I just finished a 1771 MVI for the PLC 5. The Prosoft tech support guys were helpful.