IBM System/360 System Programmer's Guide

Extent M (1 byte)
specifies, for direct-access or telecorr.munications devices, which
extent entry in the data extent block is associated with tne
channel program. (0 indicates the first extent; 1 indicates the
second, etc.)
BBCCHER (7 bytes)
specifies, for direct-access devices, the seek address for tne
programmer's channel program.
Event Control Block Fields
You must define an Event control tlock as a 4-byte area on a
full-word boundary. When the channel program has been completed, the
input/output supervisor places a' completion cede containing status
information into the event control block (Figure 11). Before examining
this information, you must test for the setting of the "Complete Bit."
If the complete bit is not on, and the problem program cannot perform
other useful operations, you should issue a WAIT macro-instruction that
specifies the event control block. Under no circumstances may you
construct a program loop that tests for the complete bit.
r----------T----------T------------------------------------------------,
I WAIT I Complete I Remainder of Completion Cede I
J Bi t=O I I I
I I
Bit=l I I
L __________ ~ __________ ~ ________________________________________________ J
o 1 2 31
Figure 11. Event Control Block After Posting of Completion Code
WAIT Bit
A one bit in
instruction has
teen completed.
Complete Bit
this position inJicates that the WAIT macro-
been issued, but that the channel program has not
- A one cit in this position indicates that the channel program has
teen completed; if it has not been comfleted, a. zero bit is in this
position.
Completion Code
This code, which includes the WAIT and Complete bits, may be one of
the following 4-byte hexadecimal expressions:
Code
7FOOOOOO
41000000
42000000
44000000
48000000
4FOOOOOO
Interpretation
Channel program has terminated without error.
Channel program has terminated with permanent
error.
Channel program has terminated because a
direct-access extent address has been violated.
Channel program has been intercepted because of
perrranent error associated with device end for
previous request. You may reissue t~~ inter-
cepted request.
Request element for channel program has been
maoe availatle aftEr it has been purged.
Error r~covery routines have been entered
because of direct-access error but are unable
to read horoe address or record O.
Execute Channel Program (EXCP) Macro-Instruction 95

IBM System/360 Specifications

General

Brand	IBM
Model	System/360
Category	Desktop
Language	English