Siemens S5-135U/155U - Manual (Page 157)

5-17
System Manual
C79000-G8576-C199-06
5.2 CPU 948
This section contains the hardware description and the technical
specifications of the CPU 948.
Details on programming the CPU 948 can be found in the CPU 948
Programming Guide.
5.2.1 Technical Description
This section contains information on the application, design and structure of
the CPU 948.
You can use the CPU 948 in single and multiprocessor operation in the
S5-135U/155U central controller (see Chapter 6).
There are two versions of CPU 948:
S
The CPU 948-1 offers 640 Kbytes of internal user memory (RAM).
S
The CPU 948-2 offers 1664 Kbytes of internal user memory (RAM).
A SIMATIC S5 flash EPROM memory card (known as a memory card for
short in the following) can be inserted in the CPU 948 as the storage medium
for user program and user data. The contents of the memory card are copied
into the internal RAM of the CPU upon overall reset.
The programming language is STEP 5 (LAD, CSF, STL, SCL). The CPU 948
processes all STEP 5 operations at very high speed, and uses fast
floating-point arithmetic.
The following program processing levels are possible:
S
Cyclic
S
Time-controlled (9 different timebases, real-time controlled, timeout)
S
Interrupt-driven from the S5 bus (8 process interrupts at block boundaries
via IB0 or, alternatively, 4 system interrupts)
S
Soft STOP.
The electronic circuitry of the CPU 948, including the RAM, is on two PCBs
of double Eurocard format which are screwed to each other. The two PCBs
must not be separated. The front plate width of the module is 2 2/3 standard
plug-in stations, i.e. 40 mm. In the central controller rack, the CPU 948
occupies two slots.
Application
Design
CPUs, Memory Cards, Memory Submodules, Interface Submodules