Fujitsu MBA3073 SERIES Technical Manual page 177

mode setting for synchronous transfer between the INIT and the TARG must be set to the
asynchronous mode.
(3) Procedures of the message exchange initiated by the TARG
If the TARG has recognized the synchronous data transfer to be set and if the synchronous data
transfer request is enabled by the CHANGE DEFINITION command, the TARG sends the
SYNCHRONOUS DATA TRANSFER REQUEST message to the INIT. The INIT shall return
the SYNCHRONOUS DATA TRANSFER REQUEST or MESSAGE REJECT message by
asserting the ATN signal before negating the ACK signal of the last byte of SYNCHRONOUS
DATA TRANSFER REQUEST message sent from the TARG. If the INIT cannot respond to this
message, the two SCSI devices shall select the asynchronous data transfer mode between them.
The INIT and the TARG shall continue the synchronous data transfer even if the INIT has
responded with the SYNCHRONOUS DATA TRANSFER REQUEST message. This
synchronous transfer mode shall be continued until the MESSAGE OUT phase is terminated
normally by transition of TARG to the INFORMATION TRANSFER phase (it indicates that no
parity error has been detected). If the TARG fails to receive the response by the INIT normally
after the specified number of retries, the TARG shall negate the BSY signal and shall enter the
BUS FREE phase immediately without executing another INFORMATION TRANSFER phase.
The INIT shall consider it as the unsuccessful message exchange and the two SCSI devices shall
select the asynchronous data transfer mode between them.
If the TARG enters the MESSAGE IN phase immediately after the INIT has responded with the
SYNCHRONOUS DATA TRANSFER REQUEST message, and if the TARG first sends the
MESSAGE REJECT message to the INIT, the INIT shall consider it as the unsuccessful selection
of synchronous data transfer. The two SCSI devices shall select the asynchronous data transfer
mode between them.
If the ATN signal is still true when the message is returned by the INIT in MESSAGE OUT phase,
if the TARG has normally received multiple messages in succession, and if the TARG receives the
ABORT TASK SET message after the SYNCHRONOUS DATA TRANSFER REQUEST
message, the TARG shall complete to process the SYNCHRONOUS DATA TRANSFER
REQUEST message and validate the transfer mode selection. Then, the TARG shall execute the
ABORT TASK SET message. If the TARG receives the ABORT TASK SET message before
receiving the SYNCHRONOUS DATA TRANSFER REQUEST message, the two SCSI devices
shall select the asynchronous data transfer mode between them.
(4) Valid cycle for the data transfer mode
After the exchange of SYNCHRONOUS DATA TRANSFER REQUEST message, the selected
data transfer mode and the synchronous data transfer parameters shall be kept valid on these SCSI
devices until when:
•
A TARGET RESET message is received.
•
A RESET condition (a hardware reset) occurs.
•
The data transfer mode or parameter is changed between the two SCSI devices.
•
Power turned off
•
Reception of the WIDE DATA TRANSFER REQUEST message
•
Change in the transceiver mode (e.g., LVD mode to SE mode).
170 C141-C015