Technical data

It changes if one of the following occurs:
•• another data block is opened
or
•• the program returns to a higher level block after a new data block
was opened in the inserted block (see also Section 2.4.2, Range of
Validity of Data Blocks).
Note
In the ISTACK, the address entered in the DBA register appears
under the heading "DB-ADD".
You normally access data words with the STEP 5 operations L/T DW,
L/T DR, L/T DL, L/T DD, A/O/AN/ON/=/S/R Dx.y. You can only
use these operations up to data word DW 255. However, by
manipulating the DBA register, you can use them to access data
words > 255. This is also possible with special function OB 180 (see
Section 6.15).
Examples
Example 1: Effect of the "CX DX 17" operation on the DBA register:
When DX 17 is called, the address of the memory word in which DW 0 is
stored is entered in the DBA register. In this example, the DBA is
4152H.
Note: In the ISTACK, the address entered in the DBA register appears
under the heading ’DB-ADD’.
5 words
block header
KH = 0000
KH = 0001
1516H
1517H
1518H
1519H
151AH
151BH
151CH
151DH
DW 0
DW 1
DW 2
DBA
Addresses
DX 17
.
.
.
Fig. 9-5 Using the DBA register
Access using the Address in ACCU 1
CPU 928B Programming Guide
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