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Siemens S5-135U/155U User Manual

Page 283

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6-21

System Manual
C79000-G8576-C199-06

The semaphores are used to coordinate the CPUs for access to the same I/O
address (see Programming Guides, operations SES and SEF).

Page Memory for
Data Blocks

Vector Register for
Page Selection,
Fault Register

Synchronization Area
for Operating Systems

Communication Flags

FEFFH

F7FFH

F400H

F300H

F200H

Page
No. 253

Page
No. 254

Page
No. 255

Page
No. 252

Figure 6-8

Areas of the Communication Memory on the S5 Bus

Addressing method for the page memory (vector register)

The vector register serves to form subaddresses of several memories in a
common address area. The register is an 8-bit register which is written to
under address FEFFH. It cannot be read out.

The page memory contains four pages of 1 Kbyte. An identification number
is assigned to each page. These are the numbers 252, 253, 254 and 255.

These numbers are permanently set on the COR 923C and cannot be
changed. You must not use these numbers on other modules (CP, IP) in the
same PLC otherwise double addressing will occur.

When the supply voltage is switched on, the vector register is cleared. The
vector register then has the number 0H.

The transfer of data to and from this memory is implemented with special
functions of the CPU. You can find these functions in the appropriate
Programming Guides.

The PG interface of the COR 923C can be switched over to eight different
serial interfaces via the path selection of the PG software.
The multiplex interfaces have TTL level and are wired to the other modules
via the backplane connector and backplane.

PG Multiplexer

Multiprocessor Operation/Coordinators