Siemens S5-135U/155U - Manual (Page 252)

5-112
System Manual
C79000-G8576-C199-06
5.11.5 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.”
The RS422 A/485 submodule can be inserted in the following CPU:
Interface Submodule ... For Use With ...
RS422 A/485 submodule CPU 928B
CPU 948
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):
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 5-25 RS422 A/485 Submodule: Full Duplex Operation
Apart from the transmit and receive lines, the RS422 A/485 submodule has a
number of control and signaling 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: V
A
> V
B
Logic 1 (OFF) corresponds to: V
A
< V
B
In the RS422 A/485 submodule, the interface signals are isolated from the
supply voltage of the PLC.
Application
Circuitry
CPUs, Memory Cards, Memory Submodules, Interface Submodules