Siemens SIMATIC S7-1200

Communication processor and Modbus TCP
13.5 Modbus communication
S7-1200 Programmable controller
1194 System Manual, V4.2, 09/2016, A5E02486680-AK
13.5.3.4
Modbus RTU instructions
Modbus_Comm_Load (Configure SIPLUS I/O or port on the PtP module for Modbus RTU) instruction
Table 13- 70 Modbus_Comm_Load instruction
LAD / FBD
SCL
Description
"Modbus_Comm_Load_DB"(
REQ:=_bool_in,
PORT:=_uint_in_,
BAUD:=_udint_in_,
PARITY:=_uint_in_,
FLOW_CTRL:=_uint_in_,
RTS_ON_DLY:=_uint_in_,
RTS_OFF_DLY:=_uint_in_,
RESP_TO:=_uint_in_,
DONE=>_bool_out,
ERROR=>_bool_out_,
STATUS=>_word_out_,
MB_DB:=_fbtref_inout_);
The Modbus_Comm_Load instruction configures
SIPLUS I/O or a PtP port for Modbus RTU pro-
tocol communications.
Modbus RTU port hardware options: Install up to
three CMs (RS485 or RS232), plus one CB
(R4845).
Modbus RTU SIPLUS I/O options: Install ET
200MP S7-
1500CM PtP (RS485 / 422 or RS232)
or ET 200SP S7-1500 CM PtP (RS485 / 422 or
RS232)
An instance data block is assigned automatically
when you place the Modbus_Comm_Load in-
struction in your program.