Siemens S5-135U/155U - Manual (Page 171)

5-31
System Manual
C79000-G8576-C199-06
For storage of your program, user memory in the form of RAM is integrated
on the board. You can store up to 64 x 2
10 bytes of code and data blocks here.
For data blocks, the CPU 928B additionally has an integrated DB RAM of
46 3/4 x 2
10 bytes.
As an external memory medium for user programs and user data, you can use
a memory card 374 with Flash EPROM.
There are two independent interfaces on the front of the CPU 928B.
You can connect programmers and OPs to the first interface. This PG
interface SI1 is permanently installed on the CPU.
You can use PG interface SI1 either via the front connector of the CPU 928B
or via the front connector of the 923C coordinator module.
Note
Simultaneous operation of PG interface SI1 via the front connector of the
CPU 928B and of the coordinator is not possible. Electrically, it is merely a
PG interface which can be operated via two different terminals. Switching
the programmer online without a job request is already sufficient to operate
the interface. If you wish to utilize a second PG interface for connection of a
PG or OP, the connection must be made via the second PG interface with the
PG submodule.
Apart from PG interface SI1, the second interface SI2 can also be used as a
PG interface in parallel with the first one. You can only use the second PG
interface via the front connector of the PG submodule on the CPU 928B.
A detailed description of operations with the two PG interfaces can be found
in the CPU 928B -3UB21 Programming Guide.
The connection to the PG can be established with the CPU in any operational
state.
User Memory
Memory Card
PG Interface SI1
CPUs, Memory Cards, Memory Submodules, Interface Submodules