Siemens S5-135U/155U - Manual (Page 212)

5-72
System Manual
C79000-G8576-C199-06
You require a user memory submodule (RAM or EPROM) for storage of your
program. You can store up to 64 x 2
10 bytes of code and data blocks here.
For data blocks, the CPU 922 additionally has an integrated DB RAM of
22 x 2
10 bytes.
Note
The DB RAM is only loaded with DB/DX blocks when the RAM submodule
is full or an EPROM submodule is inserted.
A description of the memory submodules can be found in Sections 5.9 and
5.10; order numbers are given in the ordering information.
There is an interrupt line (IR) in the S5-135U/155U PLC for each CPU. It
can be used when the reaction to one or more events must occur with higher
priority than the reaction to other events.
To process an interrupt, cyclic program processing is interrupted and the
program stored in OB 2 is inserted. Refer to the CPU 922 Programming
Guide for further details.
This interrupt-driven program processing is only possible using an
interrupt-capable digital input module (e.g. 6ES5 432-...) or a suitably
operating CP/IP module.
User Memory
Process Interrupt
Processing
CPUs, Memory Cards, Memory Submodules, Interface Submodules