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1.11.3 COMMAND phase
In COMMAND phase, the drive transmits the command receiving from the initiator to the
enclosure.
Because the data bits are 4 bits width, the drive has to transmit the data even times.
(1)
COMMAND Protocol
The drive communicates with the enclosure as shown in Figure 1.19.
(a) ; The drive asserts –DSK_WR and indicates to the enclosure that the valid data is on
D (0:3).
(b) ; The enclosure asserts –ENCL_ACK after receiving the data.
(c) ; The drive negates –DSK_WR and the data by –ENCL_ACK being asserted.
(d) ; The enclosure negates –ENCL_ACK by –DSK_WR being nagated.
(2)
Definition of COMMAND bytes
If the drive acknowledges the drive should issue COMMAND to the enclosure after receiving
SCSI command, then transmits the COMMAND as shown in Table 1.18.
byte 0
Page Code
byte 1
Reserved except bit 0 (data transfer direction in SEND
DIAG.)
byte 2
Parameter Length high byte in SEND DIAG.
byte 3
Parameter Length low byte in SEND DIAG.
COMMAND bytes length is always four bytes.
– Page code in byte 0 is defined as SES page for communicating with the enclosure.
– Bit 0 in byte 1 defines the direction of the data transfer.
0 ...... from the drive to the enclosure
1 ...... from the enclosure to the drive
– Parameter Length in byte 2 and byte 3 defines data length. The value "0000h" is used when
receiving the data (Receive Diagnostic Result command).
Figure 1.19 COMMAND, WRITE phase
Table 1.18 COMMAND bytes definition
C141-E054-02EN
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