Fujitsu MAN3184 SERIES Specifications page 149

If the responding SCSI device is able to receive data successfully with these values (or smaller
periods or larger REQ/ACK offsets or both), it returns the same values in its PARALLEL
PROTOCOL REQUEST message. If it requires a larger period, a smaller REQ/ACK offset, or a
smaller transfer width in order to receive data successfully, it substitutes values in its PARALLEL
PROTOCOL REQUEST message as required, returning unchanged any value not required to be
changed. Each SCSI device when transmitting data shall respect the negotiated limits set by the
other's PARALLEL PROTOCOL REQUEST message, but it is permitted to transfer data with
larger periods, smaller synchronous REQ/ACK offsets, or both. The completion of an exchange of
PARALLEL PROTOCOL REQUEST messages implies an agreement as shown in Table 2.12
If the responding SCSI device does not support the selected protocol option it shall clear as many
bits as required to set the protocol option field to a legal value that it does support.
If there is an unrecoverable parity error on the initial PARALLEL PROTOCOL REQUEST
message the initiating SCSI device shall retain its previous data transfer mode and protocol
options. If there is an unexpected bus free on the initial PARALLEL PROTOCOL REQUEST
message the initiating SCSI device shall retain its previous data transfer mode and protocol
options.
Table 2.12
Responding SCSI device PARALLEL
PROTOCOL REQUEST response
Non-zero REQ/ACK offset
REQ/ACK offset equal to zero
Non-zero TRANSFER WIDTH
EXPONENT
TRANSFER WIDTH equal to zero
Protocol options equal to 0h and
transfer period factor equal to 9h
IU_REQ, DT_REQ, and QAS_REQ
Equal to zero
DT_REQ equal to one
IU_REQ, and DT_REQ equal to one
MESSAGE REJECT message
Parity error (on responding message)
Unexpected bus free
(as a result of the responding message)
No response
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PARALLEL PROTOCOL REQUEST message implied agreement
Synchronous transfer (i.e., Each SCSI device transmits data
with a period equal to or greater than and a REQ/ACK offset
equal to or less than the negotiated values received in the
responding SCSI device's PPR message).
Asynchronous transfer
Wide transfer (i.e., the initiator and the target transmit data with
a transfer width equal to the responding device's transfer
width). If the initiating SCSI device does not support the
responding SCSI device's TRANSFER WIDTH EXPONENT
then the initiating SCSI device shall MESSAGE REJECT the
PPR message.
Eight-bit data
Eight-bit/asynchronous data transfer with PROTOCOL
OPTIONS field set to 0h
ST DATA IN and ST DATA OUT phases to transfer data
DT DATA IN and DT DATA OUT phases transfer data with
IU RC
DT DATA IN and DT DATA OUT phases with information
units
Eight-bit/asynchronous data transfer with PROTOCOL
OPTIONS field set to 0h
Eight-bit/asynchronous data transfer with PROTOCOL
OPTIONS field set to 0h
Eight-bit/asynchronous data transfer with PROTOCOL
OPTIONS field set to 0h
Eight-bit/asynchronous data transfer with PROTOCOL
OPTIONS field set to 0h
C141-E123-01EN
Implied agreement