Technical data

•• Access to DBs with a length greater than 261 words (five words

header) over the whole length of the DB. Using OB 180, you can

move an "access window" of 256 data words over the length of the

data block.

•• Handling data structures

A data block can be divided into several data records of the same

length and with the data arranged in the same order. This is known

as structuring the data block. A data block structured in this way

might, for example, contain the data of several subprocesses, with

a temperature value in the first data word, a pressure in the second

and other values for the subprocess in the remaining data words.

Using OB 180, you can access the data of each subprocess using

the same operations (e.g. L DD, S D, T DR etc.), by loading the

DBA register with the start address for the subprocess.

In contrast to other substitution mechanisms, (substitution =

indexed parameter assignment) you obtain simpler and faster

subroutines.

Function

With OB 180, the starting address of the current data block is shifted

by a specified value. In doing so, account is taken of the fact that the

remaining available length of the DB has to be reduced (the DBA and

DBL registers are loaded in correspondence to the shift).

Note

Before you call OB 180, a data block (DB or DX) with an

adequate length must already be open.

Parameters ACCU-1-L

offset (number of data words, by which you want to shift the data

block start address),

possible values: 0

< ACCU-1-L < DBL

OB 180: Accessing Variable Data Blocks

CPU 928B Programming Guide

C79000-B8576-C898-01

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