105BCommunication processor
12.5 Modbus communication
S7-1200 Programmable controller
608
System Manual, 11/2011, A5E02486680-05
Table 12- 72 MB_MASTER execution condition codes (Modbus protocol errors)
1
STATUS (W#16#)
Response code from
slave
Modbus protocol errors
8380
-
CRC error
8381
01
Function code not supported
8382
03
Data length error
8383
02
Data address error or address outside the valid range of the
DATA_PTR area
8384
Greater than 03
Data value error
8385
03
Data diagnostic code value not supported (function code 08)
8386
-
Function code in the response does not match the code in the request.
8387
-
Wrong slave responded
8388
-
The slave response to a write request is incorrect. The write request
returned by the slave does not match what the master actually sent.
1
In addition to the MB_MASTER errors listed above, errors can be returned from the underlying PtP communication
instructions.
See also
Point-to-Point instructions (Page 532)
12.5.3.3
MB_SLAVE
Table 12- 73 MB_SLAVE instruction
LAD / FBD
SCL
Description
"MB_SLAVE_DB"(
MB_ADDR:=_uint_in_,
NDR=>_bool_out_,
DR=>_bool_out_,
ERROR=>_bool_out_,
STATUS=>_word_out_,
MB_HOLD_REG:=_variant_inout_);
The MB_SLAVE instruction allows your
program to communicate as a Modbus slave
through a PtP port on the CM (RS485 or
RS232) and CB (RS485). When a remote
Modbus RTU master issues a request, your
user program responds to the request by
MB_SLAVE execution. STEP 7 automatically
creates an instance DB when you insert the
instruction. Use this MB_SLAVE_DB name
when you specify the MB_DB parameter for
the MB_COMM_LOAD instruction.