how read data from modbus read_var function

[saruans 1]

hello,

Somebody have suggest how need read data from slave using modbus RTU. I am using M241 PLC and read_var function. The picture you can see my PLC program. The data of slave is placed 3394 address. Then I try to read, always "READ_VAR" function get "CommError" which number is 254 that means "The detected operation error contains protocol- specific code"  and "OpenError" which number is 3 that means I don't know. How need read from slave data, which modbuss adress is 3394?

Edited 28 Apr 2022 by saruans