Master Doesn't see Holding Register

[Tom_ 0]

Dear Engineerds,

 

My Master (non siemens) doesn't see the Holding Registers of the Slave (S7-1200) plc. However the Q coils are fine and all Diagnostics don't show errors.

The Hardware:

S7-1200 – CPU 1215C

CM PtP – CB1241 RS485 (6ES7 241-1CH30-1XB0) - Half Duplex RS584

 

Firmware:

Modbus_Comm_Load (V3.1)

Modbus_Slave (V4.0)

 

I've tried with various DB, UDTs and manipulating HR_Start_offset parameter with no success. Could you advise what am I possibly missing?

Modbus_Comm_Load_DB_Snapshot.xlsx

Modbus_Slave_DB_Snapshot.xlsx

[Ragib Ur Rahman 1]

which DB you have created for Slave Registers and how did you linked it to MODBUS_Slave Block.

Please provide screenshot of it

[Tom_ 0]

Dear Ragib,

 

I've attached the files below. Please keep in mind I've tried with different data blocks, I've tried with Custom UDTs, Tried with Array of Int, Word etc.

I noticed that other working projects use Modbus_Comm_Load V2.1 and Modbus_Slave V2.1

could this be an issue?

[Tom_ 0]

Answer:

CB1241//CM1241 modules are legacy modules which use old version of modbus instructions (ver 2.1)