Control Block - Adaptec AHA-1740A Technical Reference Manual

EISA-to-Fast SCSI Host Adapter

Control Block

The control block is a 48-byte structure created and maintained in shared memory by
software in the system unit. It is used to convey requests to the host adapter.
F E D
CDB Length
CDB Byte 1
CDB Byte 3
CDB Byte 5
CDB Byte 7
CDB Byte 9
CDB Byte 11
Fields that are empty are reserved and should be set to zero.
C B A 9 8
Command Word
Flag Word 1
Flag Word 2
Data or Scatter/Gather List Pointer
Data or Scatter/Gather List Length
Status Block Pointer
Chain Address
Sense Information Pointer
Data Checksum
Enhanced Mode Firmware Description
7 6 5 4 3
Sense Length
CDB Byte 0
CDB Byte 2
CDB Byte 4
CDB Byte 6
CDB Byte 8
CDB Byte 10
2 1 0 Byte
Offset
00
02
04
06
08
0A
0C
0E
10
12
14
16
18
1A
1C
1E
20
22
24
26
28
2A
2C
2E
6-3