Siemens SIMATIC CP 440 Manual page 76

Configuring and Parameterizing the CP 440
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
Operating Mode Specifies whether the
X27 (RS 422/485) interface is to
be run in full-duplex mode
(RS 422) or half-duplex mode
(RS 485).
(See also Section 2.2.2).
Initial State of None:
the Receive
This setting only makes sense
Line (see also
for bus-capable special
Figure 5-1)
drivers.
Signal R(A)5 Volt, Signal
R(B)0 Volt:
Break evaluation is possible
with this initial state. Cannot
be set with "Full Duplex
(RS422) Four-Wire Mode
Multipoint Master" and "Half
Duplex (RS485) Two-Wire
Mode")
Signal R(A)0 Volt, Signal
R(B)5 Volt:
This initial state corresponds
to the idle state (no sender
active). Break evaluation is not
possible with this initial state.
5-12
Description
Point-to-point connection CP 440 Installation and Parameter Assignment
Value Range
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 connection 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.
None
Signal R(A)5 Volt Signal
R(B) 0 Volt (Break
Evaluation)
Signal R(A)0 Volt
SignalR(B)5 Volt
Default Value
Full Duplex
(RS 422)
Four-Wire
Mode Point
to Point
Depends on
the operating
mode set
A5E00057742-02