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SCSI Interface Overview
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Message Hex
Code
Definition
No
Operation
08h
This message has no effect and is ignored.
2.3.6
Extended messages
The following table lists extended SCSI messages and their definitions.
Hex Code
Message
Definition
Synchronous
Data Transfer
Request
01h
This message negotiates an agreement between the initiator and
the drive on which is the best data period and offset.
If the message is received after selection and before command
phase, it will then go to Message In phase and respond with a valid
response to complete the negotiation.
If the message is received at any other time, a Message Reject is
sent in response.
Wide Data
Transfer
Request
03h
This message negotiates an agreement between the initiator and
the drive on which is the best data width – 8-bit narrow or 16-bit
wide.
If the message is received after selection and before Command
phase, it will then go to Message In phase and respond with a valid
response to complete the negotiation.
If the message is received at any other time, a Message Reject is
sent in response.
Parallel
Protocol
Request
04h
This message negotiates an agreement between the initiator and
the drive on which is the best data transfer period, offset, width and
type. This is the message to request DT (Ultra160) synchronous
transfers.
The drive will never initiate a Parallel Protocol Request, but will
expect the initiator to do so.
If the message is received after selection and before Command
phase, it will then go to Message In phase and respond with a valid
response to complete the negotiation.
If the message is received at any other time, a Message Reject is
sent in response.
2.3.7
Parallel Protocol Feature Support
The following table describes the Ultra-160 Parallel Protocol features supported.
Ultra 160 Feature
Description and support
FRC_SM
Free running clock, precompensation, deskewing and P1 phase pacing
are not supported
QAS_REQ
Quick arbitration and selection is not supported
DT_REQ
Double transition transfers are supported
IU_REQ
Information units are not supported
2.3.8
Parity errors
The following table describes the operation for each of the possible cases of parity
error.
State or Phase
Description
Bus Free State
The drive does not detect nor react to parity errors on the SCSI bus while
the drive is in a bus free state.
Summary of Contents for LTO 4
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