Seagate Ultra 320 - Manual (Page 61)

Parallel SCSI Interface Product Manual, Rev. A ) 47
Table 20 defines valid combinations of HOLD_MCS and other fields.
2.12.8.5 WR_FLOW
The SCSI initiator port shall set WR_FLOW to one to indicate that the SCSI target port should enable write flow
control during write streaming. In response, the SCSI target port shall set WR_FLOW to one if it is capable of
write flow control and zero if it is not.
The SCSI initiator port shall set WR_FLOW to zero to indicate that the SCSI target port shall disable write flow
control during write streaming. In response, the SCSI target port shall set WR_FLOW to zero. Write streaming
and write flow control only occurs during information unit transfers.
Table 20 defines valid combinations of WR_FLOW and other fields.
2.12.8.6 RD_STRM
The SCSI initiator port shall set RD_STRM to one to indicate that the SCSI target port should enable read
streaming and read flow control. In response, the SCSI target port shall set RD_STRM to one if it is capable of
read streaming and read flow control and zero if it is not.
The SCSI initiator port shall set RD_STRM to zero to indicate that the SCSI target port shall disable read
streaming and read flow control. In response, the SCSI target port shall set RD_STRM to zero. Read stream-
ing and read flow control only occur during information unit transfers.
Table 20 defines valid combinations of RD_STRM and other fields.
2.12.8.7 RTI (Retain Training Information)
The SCSI initiator port shall set RTI to one to indicate it is capable of saving paced data transfer training infor-
mation and to indicate that the SCSI target port does not need to retrain on each connection. In response, the
SCSI target port shall set RTI to one if it is capable of saving paced data transfer training information and zero
if it is not.
The SCSI initiator port shall set RTI to zero to indicate it is not capable of saving paced data transfer training
information and to indicate the SCSI target port shall retrain on each connection. In response, the SCSI target
port shall set RTI to zero.
Table 20 defines valid combinations of RTI and other fields. For negotiated transfer periods slower than Fast-
160 the RTI bit shall be set to zero.
2.12.8.8 PCOMP_EN
The SCSI initiator port shall set PCOMP_EN to one to indicate that the SCSI target port shall enable precom-
pensation on all signals transmitted during DT DATA phases. The SCSI initiator port shall set PCOMP_EN to
zero to indicate that the SCSI target port shall disable precompensation.
The SCSI target port shall set PCOMP_EN to one to indicate that the SCSI initiator port shall enable precom-
pensation on all signals transmitted during DT DATA phases. The SCSI target port shall set PCOMP_EN to
zero to indicate that the SCSI initiator port shall disable precompensation.
Table 20 defines valid combinations of PCOMP_EN and other fields. 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.