Hello Everyone,

I am facing an issue with the basic functionality of the Modbus RTU communication blocks for ET200SP CM ptp module (6ES7 137-6AA00-0BA0) with S7-400H

I am trying to establish master RTU communication using the FB640 (modbus_comm_load) and FB641 (modbus_master)... 

when enabling the REQ for FB640 (modbus_comm_load) I am receiving the DONE bit and The following STATUS = 7000... so I assume this block is working fine.

after that I enable the REQ for FB641 (Modbus_Master) and only receive the BUSY bit and the following STATUS = 7001 , which means Block is "Initial call after request started". and this is not a very helpful status.

the modbus device information i am trying to access is as follows :

Baudrate: 19200
bits :8
Stop bit :1
ID : 7
Starting register : 100 -------> inserting this one as 40100 = 9CA4
Length : 1  "Only trying to read one register"

I have attached the information of my setup in a zip file which includes:
- HW configuration "overview"
- CM Ptp Configuration
- Variable Table for the functions
- PLC Rtu communication function "printed"

So please if anyone has any idea how to resolve this , I would appreciate it 

thank you 

Cheers!