Table of Contents
Advertisement
Flags 2 (1 byte)
is used only by the system.
First Two Sense Bytes (2 bytes)
are placed into the input/output block by the system
when
a
unit
check occurs.
ECB Code (1 byte)
indicates
the
first
byte
of the conpletion code for the channel
program.
The system places this code in the high order byte of the
event control block when the channel program
is
posted
complete.
The
completion
codes
and
their meanings are listed under "Event
Control Block Fields."
ECB Address (3 bytes)
specifies the address of the 4-byte event control
block
that
you
have provided.
Flags 3 (1 byte)
is used only by the system.
Channel status Word (7 bytes)
indicates
the
low
order
seven bytes of the channel status word,
which are placed into this field each time a channel end occurs.
SIO Code (1 byte)
indicates, in the four low-order bits, the instruction
length
and
condition
code
for
the SIO instruction that the systerr issues to
start the channel program.
Channel Program Address (3 bytes)
specifies the
starting
address
of
the
channel
program
to
be
executed.
Reserved (1 byte)
is used only by the system.
DCB
~ddress
(3 bytes)
specifies
the address of the data control block of the data set to
be read or written by the channel program.
Reposition Modifier (1 byte)
is used by the system for volume repositioning
in
error
recovery
procedures.
Restart Address (3 bytes)
is used by the system to indicate the starting address of a channel
prograro
that
performs
special
functions
for
error
recovery
procedures.
The
system
also
uses
this field in procedures for
making
request
elements
available,
as
explained
under
"Error
Recovery Procedures for Related Channel Prcgrams."
Block Count Increment (2 bytes)
specifies,
for
magnetic tape, the amount by which the block count
(BLKCT) field in the device dependent portion of the
data
control
block is to be incremented.
You may alter these bytes at any time.
For
forward
operations,
these
bytes
should
contain
a
binary
positive integer (usually
+
1);
for
backward
operations,
they
should contain a binary negative integer.
When these bytes are not
used, all zeros must be specified.
Error Counts (2 bytes)
94
indicates
the
number
of
retries attempted during error recovery
procedures.
Advertisement
Table of Contents
