Technical data

Block storage The programmer stores all programmed blocks in the program
memory in the order in which they are transferred (Fig. 2-2). The
programmer function "Transfer data blocks B" transfers first the code
blocks then the data blocks to the PLC. In RAM mode, the RAM card
is first to be filled with data blocks after transfer of the code blocks
and then the remaining data blocks are written into internal DB RAM.
The start addresses of all stored blocks are placed in data block DB 0.
Alternative loading (only in the
case of Version -3UB12)
By setting bit 0 in system data word RS 144, you can load data blocks
first into internal DB RAM first (i.e. as long as space is available)
("Alternative loading" - see Chapter 8/RS 144). Data blocks are
transferred to the RAM card only when the DB RAM has been filled.
Correcting and deleting
blocks
When you correct blocks in "RAM mode", the old block is declared
invalid in the memory and a new block is entered.
Similarly, when blocks are
deleted, they are not really deleted, instead
they are declared invalid. Deleted and corrected blocks therefore
continue to use up memory space.
Note
You can use the COMPRESS MEMORY online function to make
space for new blocks. This function optimizes the utilization of
the memory by deleting blocks marked as invalid and shifting
valid blocks together. Compression is handled separately
according to memory card and internal RAM (see Section 11.2.2).
Location of blocks
in the user memory
Address 0
FB1
OB1
SB10
DB1
PB1
PB2
Fig. 2-2 Example of block storage in the user memory
STEP 5 Programming Language
CPU 928B Programming Guide
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