Siemens Simatic S7-400

Operating mode/initial state of the receive line
The table below contains descriptions of the operating mode/initial state of the receive line for
the X27 (RS 422/485) interface.
Table 5-9 X27 (RS 422/485) Interface (ASCII Driver)
Parameter Description Value Range Default Value
Operating mode Speci󹪝es whether the X27 (RS 422/485)
interface is to be run in full-duplex mode
(RS 422) or half-duplex mode (RS 485).
• Full Duplex (RS 422) Four-Wire
Mode Point-to-Point
Operating mode for point-to-point
communication in four-wire
mode
• Full Duplex (RS 422) Four-Wire
Mode Multipoint Master
Operating mode for multipoint
communication in four-wire mode
if the CP is a master.
• Full Duplex (RS 422) Four-Wire
Mode Multipoint Slave
Operating mode for multipoint
communication in four-wire mode
if the CP is a slave.
• Half Duplex (RS 485) Two-Wire
Mode
Operating mode for point-to-point
or multipoint communication in
two-wire mode. The CP can be a
master or slave.
• Full Duplex (RS
422) Four-Wire
Mode Point to
Point
Initial state of re‐
ceive line
none:
This setting only makes sense with bus-
capable special drivers.
R(A) 5V / R(B) 0V
Break evaluation is possible with this in‐
itial state. (Cannot be set with "Full Du‐
plex (RS422) Four-Wire Mode Multipoint
Master" and "Half Duplex (RS485) Two-
Wire Mode")
R(A) 0V / R(B) 5V:
This initial state corresponds to the idle
state (no sender active). Break detection
is not possible with this initial state.
• None
• R(A) 5V / R(B) 0V (break detection)
• R(A) 0V / R(B) 5V
• Depends on the
operating mode
set
Con󹪝guring and Parameter Assignment the CP 440
5.4 Con󹪝guration data
Point-to-point connection CP 440 Installation and Parameter Assignment
62 Equipment Manual, 03/2022, A5E00057742-AE