Basic Principles of Serial Data Transmission
2.8 Configuration data
CP 341 Point-to-Point Communication, Installation and Parameter Assignment
92
Manual, 09/2008, A5E02191071-01
X27 (RS 422/485) interface
You will find a description of the parameters for the X27 (RS 422/485) interface in the table
below.
Table 2- 15 X27 (RS 422/485) interface (ASCII driver)
Parameters
Description
Range of values
Default value
Operating mode
Specifies whether the X27 (RS 422/485)
interface is to be operated in full-duplex
(RS 422) or half-duplex (RS 485) mode.
(See also Serial Transmission of a
•
Full-duplex (RS 422)
four-wire mode
•
Half-duplex (RS 485)
two-wire mode
Full-duplex (RS 422)
four-wire mode
Receive line initial state None: This setting only makes sense with
bus-capable special drivers.
R(A) 5V / R(B) 0V: This default setting
supports break detection in "Full-duplex
(RS 422) four-wire mode".
R(A) 0V / R(B) 5V: This default
corresponds to idle state (no senders
active) in "Half-duplex (RS 485) two-wire
mode". Break detection is not possible in
this initial state.
(also see the following figure)
•
None
•
R(A) 5V / R(B) 0V
1
•
R(A) 0V / R(B) 5V
R(A) 5V / R(B) 0V
1
(In "Half-Duplex
(RS 485) Two-Wire
Mode", the default
setting is R(A) 0V /
R(B) 5V.)
Delete CP receive
buffer at startup
You can specify whether the CP receive
buffer should be deleted on startup or
existing (old) message frames should be
sent to the CPU.
•
Yes
•
No
No
1
Only in the case of "Full-Duplex (RS 422) Four-Wire Mode".
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