Register 8:
DBL = Data Block Length
In addition to the DBA register, a DBL register is loaded every time a
data block is called. It contains the length (in words) of the data block
called, without the block header. The DBL register is set to ’0’ before
each OB 1 call.
DBL register is retained, when
•• program execution is continued in a different block following a
jump statement (JU/JC)
or
•• a different program execution level is nested in.
It changes when
•• a different data block is opened
or
•• program execution returns to a higher order block after a new data
block is opened in the called block (refer to Section 2.4.2).
Note
You can change the DBA and DBL registers using LIR operations
to address data block addresses higher than 255. The DBA
register contains paragraph addresses. Make sure that a change
in the DBA register does not automatically cause a change in the
DBL register and vice-versa. This would mean that transfer
error monitoring is no longer guaranteed.
On the CPU 948, changes in the DBA/DBL registers are undone,
as soon as the current block is completed (BSTACK entries).
Manipulations on the DBA/DBL registers are therefore only
effective in the block in which they were made.
Memory Access via Address in ACCU 1
CPU 948 Programming Guide
C79000-G8576-C848-04
9 - 13
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