User memory
You require a user memory submodule (RAM or EPROM) for storage
of your program. You can store up to 64 Kbytes of code and data
blocks here. For data blocks, the CPU 922 additionally has an
integrated DB RAM of 22 Kbytes.
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 5.6
and 5.7; order numbers are given in the ordering information.
Process interrupt
processing
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.
CPU 922
System Manual
5 - 44
C79000-B8576-C199-03
