Technical data

6.14 OB 170: Read Block Stack (BSTACK)

Starting with OB 1 or FB 0, the block stack contains all the blocks

that have been called in sequence and that have not yet been

completely processed.

Function

Using the special function organization block OB 170, you can read

the entries currently in the BSTACK into a data block. In this way,

you can find out how many entries are currently in the BSTACK and

how much space is still available for further entries.

For each entry, you obtain the return address (step address counter =

SAC), the absolute start address of the data block valid in this block

(DBA) and its length (number of data words = DBL).

Note

Before you call OB 170, you must first open a data block (DB or

DX)

with sufficient length. Four data words are required for

each BSTACK entry.

Parameters

Accus

a) ACCU-2-L

Number of the data word (DW n) from which the entries are to be

stored in the open DB (offset)

ACCU-1-L

Required number of BSTACK elements;

Possible values: 1 - 62

Example: if ACCU-1-L contains the value "1", you obtain the last

BSTACKentry, if it contains "2", you obtain the last

and one before last etc.

OB 170: Read Block Stack (BSTACK)

CPU 928B Programming Guide

C79000-B8576-C898-01

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