User`s manual

siop_struc (Command Structure)
SBCSCSI/D1 B-5
B
Another use of this bit is when sending a request sense command in response
to a CHECK status received for some command to a device. The request sense
command must be sent before any other commands to prevent the CHECK
condition from being cleared before the user can find out the reason for the
CHECK status.
Bit 16 -- DEVRST
initiator mode
If set, the command structure allocated to the Firmware contains a bus device
reset message in the first byte of the message out field. To issue the bus device
reset message to a SCSI device the Firmware selects with ATN asserted and
when the target responds to selection and transitions to the message out phase,
the Firmware responds to that phase by sending the message in the message-
out field.
The user must initialize the command structure for this sequence. The user
must install the SCSI address, LUN, message-out length, message-out pointer,
and message byte. (The message-out pointer field can point to the message-
out field of the structure if that is where the user installed the bus device reset
message.) Additionally, the user must clear the NO_ATN bit, set the MOBUF
bit, and set the DEVRST bit in the command control field. The DEVRST bit is
used for error checking and is not tested except for unexpected disconnects.
In the case of an unexpected disconnect, if the DEVRST bit is set, the Firmware
resolves the device reset condition. For a device reset condition all pending
commands to the target LUN are returned. Internal synchronous data rate
information is set to asynchronous. Internal tagged command queuing
information is set to non-support.