Data Re-Transfer; Buffer Parity Errors - Tandberg Data SLR7-140 PROGRAMMER Manual

Tandberg Data
2.7.8.

Data Re-transfer

As a part of its bus parity error handling the Drive is
able to re-transfer
number of times.
When receiving
optionally check for parity errors in the data received.
When the complete data burst has been transferred the
Drive changes from the data-out phase to the message-in
phase. A RESTORE POINTERS message is then transferred to
the Initiator. The Initiator should in response to this
message reset its data pointer to where it was when the
Drive instructed it to save its pointer the last time
(with the SAVE DATA POINTER message sent each time the
Drive disconnects)
received set the pointer back to where it was when the
write type command was issued. The Drive then re-enters
the data-out phase and transfers the last burst of data
once more. The whole process can be repeated a number of
times as long as the Drive detects parity errors in the
received data.
When transferring data to the Initiator in read mode the
Initiator may check for parity errors in the received
data. When a
Initiator may assert the ATN. After having transferred
the complete data burst the Drive will honor the ATN
condition by going
message-out phase. A message is then transferred from
the Initiator. If this message is an INITIATOR DETECTED
ERROR message the Drive will assume that the Initiator
wants to have the last burst of data transferred once
more. The Drive then goes to the message-in phase and
transfers a RESTORE
should then reset its data pointer to where it was when
the Drive instructed it to save its pointer the last
time (with the SAVE DATA POINTER message sent each time
the Drive disconnects) or if no such message has been
received set the pointer back to where it was when the
read type command was issued. The Drive then re-enters
the data-in phase and transfers the last burst of data
once more. The whole process can be repeated a number of
times as long as the Initiator asserts ATN during the
data transfer.
See also the sub-section on Bus Parity Error Handling in
section 7 for further information.
2.7.9.

Buffer Parity Errors

The Drive is able to check for internal parity errors in
its data buffer system. All data paths include a parity
bit for every 8 bits of data. See the sub-section on
Buffer Parity Error Handling in section 7 for details.
2-28 Tandberg SLR Product Line SCSI Functional Specifications
the last
data in write
or if no such
parity error has
from the
POINTERS message.
About Tape Streamers
transferred burst
mode the Drive
message has
been detected
data-in phase to
The Initiator
any
may
been
the
the