User’s Guide 21020285 D
Chapter 7 Board-control Commands
Extended Unit Options (18H) Page 7 - 45
Extended Unit Options (18H)This command, in either initiator or target mode, is designed as an enhancemen t
to the Unit Options command. The primary difference between the commands
is the opportunity to select 16 bytes of Sense Data to be returned pe r unit, instead
of the eight offered in the Unit Options command.
Another difference is that the Extended Unit Options for the SCSI device are
built into a Data Structure whose address is simply passed in the command.
Command
Format
The format of the Extended Unit Options command is as follows:
Description of
Fields
Each of the fields of the Parameter Block are described below:
Command Identifier
The Command Identifier field is used to identify the Status Block associated
with a Parameter Block. It must be a unique value.
Adapter ID
This is a Board-control command. The value in this field must be FFH.
Address Modifier
This is the value to be used by the adapter on the Addr ess M odifier lines when
reading the Extended Unit Options Data Structure from memory.
VME Memory Address
This is the system memory address at which you have built the Extended Unit
Options Data Structure.
Command Code
The value for this field will always be 18H to indica te a Exte nded Unit Opt ions
command.
The format of the Data Structure to be used for the Extended Unit Options
command is illustrated on the following pages.
Address
Offset Byte Memory Address
Offset + 0Offset + 1Offset + 2Offset + 3
00H Command Identifier
04H Reserved Addr. Mod. Adapter ID = FFH
08H VME Memory Address
0CH Reserved
10H Command = 18H Reserved
14H Reserved
18H Reserved
Table 103: Extended Unit Options Parameter Block