Technical data

3.3 Storing Program and Data Blocks

You must load your program into the user memory so that the CPU

can process it. As program memory you can use a plug-in submodule

(optional either RAM or EPROM) and the DB-RAM.

Different storage types

•• If you use a plug-in RAM submodule you can transfer your

program directly from the programmer to the CPU.

You can change the contents of a RAM submodule quickly and

easily. A central back-up battery prevents your program being

deleted in the memory if the power goes off.

All programmed blocks are stored in random order in the RAM

(see Section 2.1.5, Fig. 2-2). If you change a block, the sequence

of the blocks in the RAM also changes.

If you use a

RAM submodule with a back-up battery, you can

remove it from the CPU without losing data. Having its own

battery protects the submodule from loss of data and ensures

that the data is retained until it is required again.

•• You can also store your complete program in plug-in EPROM

submodules

. Your program is completely protected in EPROM

submodules even when the power goes off and no back-up battery

is necessary.

You cannot change the contents of an EPROM submodule from

the PC. For this reason, data blocks that contain variable data that

have to be changed during the course of your program must be

copied from the EPROM submodule to the data block RAM of the

CPU during the first cold restart following an overall reset. You

must program this function (see special function OB 254 and

OB 255, Section 6.4.6).

•• Data blocks DB/DX are written into the DB-RAM by generating

or copying them. If you transfer data blocks from the PG to the

CPU, they are written to the DB-RAM if the RAM submodule is

full or if an EPROM submodule is plugged in.

Caution

Battery-backed RAM submodules must not be programmed via

the EPROM interface; this can damage the RAM.

When storing data blocks, please note the possibility of "alternative loading" - Section 2.1.5.

Storing Program and Data Blocks

CPU 928B Programming Guide

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