Siemens AS 235 appendix Interface modules for coupling with other systems, summary

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Coupling with other systems

Summary

Interface modules for coupling with other systems, summary

Interface module	Type of coupling	Interface	Procedure	Electrical isolation	Coupling partner
6DS1 321-8AA	Parallel,	RS 422	I/O bus interface	No	SIMATIC S5 expansion units
	bus connection
6DS1 327-8AA	Serial,	RS 485	(ET 100)	Yes	SIMATIC S5 expansion units, ET 100U
	bus connection
6DS1 333-8AB	Serial, point-to-	TTY	3964 R / RK 512	Yes, at receiver	SIMATIC S5 programmable controllers
	point connection				with CP 524 and CP 544 communica-
					tions processors
					SIMATIC S7-400 automation systems
					with CP 441-2 communications proces-
					sor
					SIMATIC S7-300 automation systems
					with CP 341 communications proces-
					sor

Summary

￿A differentiation is made for AS 235 couplings between

• coupling via the CS 275 bus and

• direct coupling via special interface modules. This section only deals with direct coupling.

The summary table lists all available interface modules for cou- pling with other systems, together with the most important fea- tures of the modules.

All interface modules are operated in a slot for I/O modules.

An important feature for differentiation is the type of coupling (parallel/serial):

• With a parallel coupling, the interface module 6DS1 321-8AA transfers all bus signals between the automation system and the coupling partner – with the exception of the level conver- sion signals TTL-RS 422-TTL – in real-time mode. The driver blocks directly access the I/O modules in the connected expansion unit with a parallel coupling.

• With a serial coupling, the interface modules themselves han- dle the data transfer with the coupling partner. Data transfer is via the transfer RAM of the interface module with a serial cou- pling.

When selecting the interface module suitable for the respective application, the following factors may be important in addition to the type of coupling partner:

•The distance to the coupling partner

•The topology of the system

•The earthing concept

•Measures which may be needed for lightning protection.

Since the parallel coupling is not electrically isolated and the RS 422 system used permits a maximum difference of 7 V between the earth potentials of the coupling partners, it is rec- ommendable to use a serial coupling for longer distances within buildings and for links between different buildings. As a result of the lower number of conductors in the cable and the electrical isolation, this facilitates any protection measures for static and dynamic differences in potential (earthing, lightning protection).

The transmission rate and thus the cycle time can be varied with

aserial coupling. However, the selected data transfer rate has an influence on the maximum distance which can been covered.

The driver blocks required for the various links are contained in the standard software of the automation system.

Coupling of other systems

The interface module 6DS1 333-8AB can be used to couple other systems (e.g. scales, data acquisition units, process chro- matographs) if the system has an appropriate interface, i.e.

20-mA current loop interface (TTY) and 3964 R / RK 512 proce- dure. Other procedures and protocols require especially pro- duced firmware. However, detailed knowledge of the module hardware, the interface to the automation system, and the driver blocks is required in this case.

We would be pleased to recommend software companies with appropriate know-how for the generation of this firmware.

7/2 Siemens PLT 111 · 1999