Basler DECS 200 communication with AB 1769-SM2

[mixguy]

Hi everyone,

i am facing problem in using Allen bradley compact logic system of the 1769-SM2 module, communicating with basler DECS-200. I wanted to read the data of holding register of 47275 - 47276. My basler Decs-200 address is 5. Therefore, the command message that i send was Device address = 5 , function code= 3 , staring register=7275 , number of register=2. However, the message block of the PLC is returning an error message of "Communication failure". Would appreciate any guidance from you guys. thanks

 

[danw2]

The message appears to be Modbus formatted message.

1) What is the physical comm link? 2 wire RS-485?

2) How is the CRC calculated? Is Modbus master a native implementation on CompactLogix so it calculates CRC? Or do you have a Modbus card and it calculates CRC? Or are you custom 'messaging' through some means?