5.8.5
RS422 A/485 Submodule
The RS422 A/485 submodule is for use exclusively in the RS422 A
mode with the RK 512 computer link, data transmission with
procedures 3964/3964R, data transmission with the "open driver".
Application
The RS422 A/485 submodule can be inserted in the following CPU:
Interface Submodule... For Use With...
RS422 A/485 sub-
module
CPU 928B
Circuitry
With the above types of communication, the RS422 A/485 submodule
can only be used in full duplex operation implemented by hardware.
The electrical characteristics are governed by EIA Standard RS422 A
(CCITT Recommendation V.11).
Shown in the following figure is the circuitry for the interface
(transmit and receive lines):
Apart from the transmit and receive lines, the RS422 A/485
submodule has a number of control and signalling lines to CCITT
Recommendation X.24 and ISO 8481. In association with the above
types of communication, however, these control and message signals
are not required and need therefore not be wired.
The RS422 A/485 is a differential voltage interface and therefore
exhibits higher rejection of interference than a TTY or V.24 interface.
The following applies to the signals to EIA Standard RS422 A (V.11):
Logic 0 (ON) corresponds to VA > VB
Logic 1 (OFF) corresponds to VA <VB
In the RS422 A/485 submodule, the interface signals are isolated from
the supply voltage of the PLC.
Device 1
GND
Device 2
GND
Shield
Shield
T(A)
T(B)
R(A)
R(A)
R(B)
T(A)
T(B)
R(B)
Figure 5-21
RS422 A/485 Submodule: Full Duplex Operation
5
Interface Submodule
System Manual
C79000-B8576-C199-03
5 - 85
