Messages26
Parallel Protocol Request
Fields:
Status
A Status byte is sent from the drive to the host during the Status phase at the end of each
command as specified in the SCSI specification, unless the command has been cleared by an
ABORT message, by a BUS DEVICE RESET message, or by a hard reset.
7 6 5 4 3 2 1 0
0 Extended Message (01h)
1 Extended Message Length (06h)
2 Parallel Protocol Request (04h)
3 Transfer Period Factor
4 Reserved (0)
5 Req/Ack Offset
6 Transfer Width Exponent
7 PComp_En RTI Rd_Strm WR_Flow Hold_MCS QAS_Req DT_Req IU_Req
Transfer Period
Factor
08h Transfer period of 6.25 ns, Paced Information Unit transfers
09h Transfer period of 12.5 ns (FAST-80). Only valid when DT transfers have
been requested
0Ch Transfer period of 50 ns (FAST-20) — LVD/SE drives only
19h Transfer period of 100 ns (FAST-10)
32h Transfer period of 200 ns (FAST-5)
Req/Ack Offset This has a maximum value of 255.
Transfer Width
Exponent
For ST transfers, this can be either 0 (Narrow) or 1 (Wide).
For DT transfers, it must be set to 1.
PComp_En Precompensation enable bit. Supported.
RTI Retain Training Information bit. Supported.
Rd_Strm 0 Read streaming and read flow control enable bit. Not supported, so the
drive will always return zero.
Wr_Flow 0 Write flow control enable bit. Not supported; the drive will always return
zero.
Hold_MCS 0 Hold Margin Control Settings bit. Not supported; the drive will always return
zero.
QAS_Req 0 QAS enable request bit. Not supported; the drive will always return zero.
DT_Req This bit determines whether DT mode has been requested, in other words,
packetized data transfers. Supported.
IU-Req Information units enabled request bit. Supported.
