IBM Professional Series User Manual

DIAGNOSE Code X'18' -- Standard
DASD I/O
Input/Output operations to FBA type DASD minidisks, of
the type used by VM/PC CMS, can be performed from a
virtual machine using Diagnose
018 . No interrupts are
returned
to the virtual machine; the instruction completes
only when the read or write operation has completed. Rx
contains the address of the minidisk;
Ry points to the
following chain
of CCWs:
DEFINE EXTENT,extent,CC,16
LOCATE BLOCK,blockid,CC,8
READ or WRITE BLOCK,data,O,n*512
or
DEV CHAR,data,O,32
Where:
extent
defines the extent of the minidisk:
DS X
DC XIOOI
DC XIOOOOI
DC F'O'
DC F'O'
DS F
blockid
MASK X'OO'=allow write
X
'
Oll=inhibit write
RESERVED
BLKSIZE=512
DEVICE OFFSET TO FIRST BLOCK
FIRST BLOCK IN MINIDISK
LAST BLOCK IN MINIDISK
defines the block(s) to read or write:
DS X
DC XIOOI
DS H
DS F
data
SUB-COMMAND X
'
Ol
l
=write
X'OS'=write/check
X
'
06
1
=read
RESERVED
NUMBER OF BLOCKS
BLOCK OFFSET WITHIN MINIDISK
the storage address of the data area to read into or
write from.
For improved performance, this data
area should not cross a page boundary.
A-12 VM/PC Users Guide

IBM Professional Series Specifications

General

Brand	IBM
Model	Professional Series
Category	Software
Language	English