Siemens S5-135U/155U - Manual (Page 203)

5-63
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 928 additionally has an integrated DB RAM of 46 x 2 10
bytes.
Note
The DB RAM is loaded with DB/DX blocks when the RAM submodule is
full or an EPROM submodule is plugged in.
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 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.
o process an interrupt, cyclic program processing is interrupted and the
program stored in OB 2 (OB for interrupt processing) is inserted.
(Refer to the CPU 928 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 CP/IP module
which operates in this way.
User Memory
Process Interrupt
Processing
CPUs, Memory Cards, Memory Submodules, Interface Submodules