System Control Blocks

Offset
16 (10) 7
17 (11) • 7
24 (18) 4
28 (le) 2
30 (lE) •• 2
30 (lE) •• 1
Bytes and Field
Alignment Name
31 (IF) ••• 1
32 (20) 8
ICBSTART
1. •• • ...
• xxx xxxx
32 (20) Byte 1
33 (21) Bytes 2- 8
INTERRUPTION CONTROL BLOCK
Hex.
Dig. Field Description, Contents, Meaning
Flag byte 3.
Flags for I/O supervisor error routine (device
dependent) •
CSW
Low order seven bytes of the last CSW. Shows channel
status for this request.
Channel program pointer
Address of the channel program to be executed.
Increment amount
Magnetic tape
Constant that is used to increment the block count
Always zero for direct access.
Indicators.
Special volume full indicator signifying end-of-tape
mark or reflective spot sensed along with a read or
write error.
(Reserved Bits) Always zero •
Reserved.
208 OS System Control Blocks (Release 21.7)
Seek Information.
This field is present for direct access devices only
The number of the DEB extent to be used for this
request. The first extent is number zero.
The seek address for this I/O request.