Ciprico Rimfire 3880 - Manual (Page 173)

User’s Guide 21020285 D
Chapter 7 Board-control Commands
Extended Unit Options (18H) Page 7 - 49
TAG - The function of this bit varies depending on whether the adapter is in
Initiator or Target Mode.
Initiator Mode
Tagged Commands
- In initiator Mode, one of the design options
offered with the SCSI-2 and SCSI-3 specification is the capability to
issue multiple simultaneous commands to each logical unit. If you have
a peripheral that is designed to this specification, you can use this bit to
tell the RF3880 adapter to negotiate for queued tagged commands. The
tag “type” is specified in the Flags-2 field of the Pass-through command
Parameter Block. Refer to Chapter 5.
0
⇒
Tagged commands not negotiated.
1
⇒
Peripheral supports tagged commands - negotiate for it.
Target Mode
Selection of Group 2 Commands
- During Target Mode
operations, the Tag bit controls whether Group 2 6- or 10-byte SCSI-2
commands are accepted.
0
⇒
6-byte commands accepted; no SCSI—2 devices configured.
1
⇒
10-byte commands accepted; SCSI—2 devices configured.
Sense Count
The RF3880 adapter automatically responds to a device Check Condition with
a SCSI Request Sense command. (Unless inhibited on a per command basis
with the IRS bit of the Flags-1 field which is embedded in the SCSI Pass-
through command Parameter Block. See Chapter 5.)
The Request Sense command, issued by the adapter to the device with the
Check Condition, can garner Sense information of up to 256 bytes. The number
returned depends on the number asked for in the SCSI Request Sense command
that is issued by the adapter. The Sense Count field is used to define the number
of Sense bytes the adapter will ask for when automatically issuing a Request
Sense command.
Valid values for this field are 0 to 32 (20H).
If more than 32 bytes of sequential sense information is requested, the count
will be set to 8 and error code A1H will be returned.
Otherwise, the value you place in the Sense Count field is used in conjunction
with the Selected Sense Bytes Fields. There are three ways you can use the
Sense Count and Selected Sense Bytes fields to get the result you want:
To receive the default —first eight bytes of Request Sense Data
• Place a zero value in Sense Count field.
• Place zeroes in all fields of Selected Sense Bytes.
To receive any sixteen bytes of Request Sense Data from the possible 256:
• Place a zero in the Sense Count field.
• Place the Sense Byte number in each of the sixteen fields of the Selected
Sense Bytes, in the order desired.