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21020285 D User’s Guide
Chapter 7 Board-control Commands
Page 7 - 46 Extended Unit Options (18H)
Extended Unit
Options Data
Structure
The Data Structure that you will use to pass the Extended Unit Option
parameters to the RF3880 adapter is similar to the format of the Unit Options
Parameter Block.
The Data Structure must contain these fields:
Description of
Fields
Each of the fields of the Data Structure are described below:
Unit SCSI ID
This field must contain a number from 0 - 15 representing a SCSI Unit on the
bus. Do not use the RF3880 adapter SCSI ID you assign with the General
Options command. (If you do you will receive the 02H (Bad Unit) error code.)
Disconnect Time-out
If you have enabled SCSI bus Disconnect with the General Options command,
this field selects — for the specified unit — the amount of time the adapter will
wait for a reconnect. If a reconnect does not occur within the time defined, the
adapter will post a time-out error (1FH) in the appropriate command Status
Block.
The time appropriate for a disconnect depends on the action and the unit
performing the task (seeks, rewinds, etc.). For this reason, the Disconnect Time-
out value is tailored per unit with a latitude of 100 milliseconds to almost two
hours. You may also choose the option of no time-out for this unit. In that case,
the device or SCSI bus must be reset to recover from the failure.
0 ⇒ No time-out occurs; SCSI bus or device must be reset to clear a failure.
Each increment ⇒ 100 milliseconds.
Note
The sequentially
recorded nature of tape
media is such that
positioning for retries
requires extra
commands. For this
reason, do not enable the
retry function for SCSI
tape devices.
Retry Limit
If retries are enabled in the Retry Control field, (discussed next) this field
specifies the maximum number of retries to attempt before reporting an error.
Once the retry limit is reached, the error condition reported with the last retry
is returned in the Status Block.
You must provide a value in this field or retries will not occur even if enabled
(in the Retry Control field).
Address
Offset
Byte Memory Address
Offset + 0 Offset + 1 Offset + 2 Offset + 3
00H Disconnect Time-out Unit SCSI ID 0
04H Select Time-out Retry Control Retry Limit
08H Reserved Reserved Sense Count Unit Flags
0CH Sense Byte # Sense Byte # Sense Byte # Sense Byte #
Status
Block #1
10H Sense Byte # Sense Byte # Sense Byte # Sense Byte #
14H Sense Byte # Sense Byte # Sense Byte # Sense Byte #
Status
Block #2
18H Sense Byte # Sense Byte # Sense Byte # Sense Byte #
1CH 0
Table 104: Extended Unit Options Data Structure