Seagate ST3285N, Product Manual, Page: 67 / 151

3.4.14 Start/Stop Unit command (1B
H
)
When the drive receives the Start/Stop Unit command, the drive either
spins up or spins down, depending on the setting of the start bit in byte 4.
If the host adapter supports disconnection, the drive disconnects when
it receives the Start/Stop Unit command and reconnects when it is up to
speed and ready.
Bit
Byte
7 6 5 4 3 2 1 0
0 0 0 0 1 1 0 1 1
1 LUN = 0 0 0 0 0 Immed
2 0 0 0 0 0 0 0 0
3 0 0 0 0 0 0 0 0
4 0 0 0 0 0 0 0 Start
5 0 0 0 0 0 0 Flag Link
Byte 1 If the immed bit is 0, the drive returns the status after it completes
the command. If the immed bit is 1, the drive returns the status
when it receives the command.
Byte 4 If the
start bit is 1, the drive spins up. If the start bit is 0, the drive
spins down.
ST3655 Family SCSI Drives Product Manual, Rev. A 57