Sony AIT-SDX800, Руководство по техническим характеристикам продукции

Страница: 47 / 204

5.SCSI Interface
SONY AIT-3Ex drive SDX-800V series Ver.1.0
5-5
5.3.1. COMMAND COMPLETE (00h)
This message is sent from a target to an initiator to indicate that the execution of a command or a series of linked
commands has completed and valid status has been sent to the initiator. After successfully sending this message,
the target goes to the BUS FREE phase by releasing BSY.
When received as a target, it will be handled as an illegal message, the unit will return MESSAGE REJECT and will
enter the status phase reporting CHECK CONDITION with the sense key set to COMMAND ABORTED.
5.3.2. EXTENDED MESSAGE (01h)
5.3.2.1. PARALLEL PROTOCOL REQUEST (04h)
PARALLEL PROTOCOL REQUEST messages are used to negotiate a synchronous data transfer agreement, a
wide data transfer agreement, and set the protocol options between two SCSI devices. Negotiations using this
message shall only be initiated by initiators. A Parallel Protocol Request message has the following format:
PARALLEL PROTOCOL REQUEST
Bit
Byte
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
5 REQ/ACK OFFSET
6 TRANSFER WIDTH EXPONENT (m)
7 RESERVED QAS_REQ DT_REQ IU_REQ
TRANSFER PERIOD FACTOR FIELD
Code Description
09h
Transfer period equals 12.5 ns (Fast-80 data is latched every 12.5 ns). This code is only
valid if the protocol options field has a value selected that supports double transition data
transfer (DT_REQ is one)
0Ah Transfer period equals 25 ns (Fast-40 data is latched every 25 ns or 30.3 ns).
0Bh Transfer period equals 30.3 ns (Fast-40 data is latched every 25 ns or 30.3 ns).
0Ch Transfer period equals 50 ns (Fast-20).
0Dh-18h Transfer period equals the period factor x 4 (Fast-20).
19h-31h Transfer period equals the period factor x 4 (Fast-10).
32h-FFh Transfer period equals the period factor x 4
For single transition (ST) synchronous data transfer the REQ/ACK OFFSET is the maximum number of REQ
assertions allowed to be outstanding before a corresponding ACK assertion is received at the target. The size of a
data transfer may be 1 or 2 bytes depending on the values in the transfer width exponent field.
For double transition (DT) synchronous data transfer the REQ/ACK OFFSET is the maximum number of REQ
transitions allowed to be outstanding before a corresponding ACK transition is received at the target. The size of a
data transfer shall be 2 bytes.