Siemens S5-135U/155U appendix 11.5 RS422 A/485 Submodule, RS422 A/485 submodule CPU 928B CPU

CPUs, Memory Cards, Memory Submodules, Interface Submodules

5.11.5RS422 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 ªopen driver.º

Application 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

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):

Device 1	Device 2
GND	GND
T(A)	T(A)
T(B)	T(B)
R(A)	R(A)
R(B)	R(B)
Shield	Shield

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: 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.

5-112	System Manual
	C79000-G8576-C199-06