Fujitsu MAW3073 SERIES Specifications page 188

The protocol options bits (PCOMP_EN, RTI, RD_STRM, WR_FLOW, IU_REQ, DT_REQ,
QAS_REQ, and HOLD_MCS) are used by the originating SCSI device to indicate the protocol
options to be enabled. The responding SCSI device uses the protocol options bits to indicate the
protocol options requested by the originating SCSI device the responding SCSI device has
enabled.
INIT shall set PCOMP_EN to one to indicate that the TARG shall enable precompensation on all
signals transmitted during DT DATA phases. The INIT shall set PCOMP_EN to zero to indicate
that the SCSI target port shall disable precompensation.
TARG shall set PCOMP_EN to one to indicate that the INIT shall enable precompensation on all
signals transmitted during DT DATA phases. The TARG shall set PCOMP_EN to zero to indicate
that the INIT shall disable precompensation.
Ports that support Fast-160 shall support enabling and disabling precompensation of their drivers.
For negotiated transfer periods slower than Fast-160 the PCOMP_EN bit shall be set to zero.
Note :
Unlike other fields and bits in the PPR message the PCOMP_EN bit is not a negotiated value;
instead, it instructs the receiving SCSI device as to whether or not precompensation is to be
disabled or enabled. Because of this, precompensation may be enabled on one of the SCSI
devices and disabled on the other SCSI device at the completion of a successful PPR
negotiation.
INIT shall set RD_STRM to one to indicate that the TARG should enable read streaming and read
flow control. In response, the TARG shall set RD_STRM to one if it is capable of read streaming
and read flow control and zero if it is not.
The INIT shall set RD_STRM to zero to indicate that the TARG shall disable read streaming and
read flow control. In response, the TARG shall set RD_STRM to zero.
Read streaming and read flow control only occur during information unit transfers.
INIT shall set WR_FLOW to one to indicate that the TARG should enable write flow control
during write streaming. In response, the TARG shall set WR_FLOW to one if it is capable of write
flow control and zero if it is not.
The INIT shall set WR_FLOW to zero to indicate that the TARG shall disable write flow control
during write streaming. In response, the TARG shall set WR_FLOW to zero.
Write streaming and write flow control only occurs during information unit transfers.
An information units enable request bit (IU_REQ) of zero indicates that information unit transfers
shall not be used (i.e., data group transfers shall be enabled) when received from the originating
SCSI device and that information unit transfers are not supported when received from the
responding SCSI device. An IU_REQ bit of one indicates that information unit transfers shall be
used when received from the originating SCSI device and that information unit transfers are
supported when received from the responding SCSI device. If the IU_REQ bit is changed from the
previous agreement (i.e., zero to one or one to zero) as a result of a negotiation the TARG shall go
to a BUS FREE phase on completion of the negotiation.
2-30 C141-C011