Siemens S5-135U/155U appendix User Memory, Memory Card

CPUs, Memory Cards, Memory Submodules, Interface Submodules

User Memory	For storage of your program, user memory in the form of RAM is integrated
	on the board. You can store up to 64 x 210 bytes of code and data blocks here.
	For data blocks, the CPU 928B additionally has an integrated DB RAM of
	46 3/4 x 210 bytes.
Memory Card	As an external memory medium for user programs and user data, you can use
	a memory card 374 with Flash EPROM.
PG Interface SI1	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.

System Manual	5-31
C79000-G8576-C199-06