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64 Cheetah 10K.7 SCSI Product Manual, Rev. D
9.5 Synchronous data transfer
The data transfer period to be used by the drive and the initiator is established by an exchange of messages
during the Message Phase of operation. See the section on message protocol in the SCSI Interface Product
Manual, part number 75789509.
9.5.1 Synchronous data transfer periods supported
In the following tables, M is the synchronous period value (in the transfer rate negotiation message) that repre-
sents the associated transfer period and transfer rate values.
Table 11 lists the synchronous data transfer periods supported by the drive in DT DATA phase. DT DATA phase
is only allowed when using the LVD interface.
Table 12 lists the synchronous data transfer periods supported by the drive in ST DATA phase. ST DATA phase
is allowed with either LVD or SE interface except as noted.
9.5.2 REQ/ACK offset
Cheetah 10K.7 SCSI family drives support REQ/ACK offset values from 7 to 63 (3Fh). Offsets of 1 through 6
are negotiated to 0 (asynchronous transfer).
9.6 Physical interface
This section describes the connectors, cables, signals, terminators and bus timing of the DC and SCSI I/O
interface. See Section 9.8 and Section 9.9 for additional terminator information.
Figures 22 and 23 show the locations of the DC power connector, SCSI interface connector, drive select head-
ers, and option select headers.
Details of the physical, electrical and logical characteristics are given in sections following, while the SCSI
operational aspects of Seagate drive interfaces are given in the SCSI Interface Product Manual.
Table 11: Synchronous DT DATA transfer periods
M (decimal)
Transfer period
(nanoseconds)
Transfer rate
(megatransfers/second)
Transfer rate
(Mbytes/second) on wide bus
8 6.25 160.0 320.0
9 12.5 80.0 160.0
10 25 40.0 80.0
12 50 20.0 40.0
25 100 10.0 20.0
Table 12: Synchronous ST DATA transfer periods
M (decimal)
Transfer period
(nanoseconds)
Transfer rate
(megatransfers/second)
10 25 40.0
1
1. This transfer rate is only allowed when using the LVD interface.
12 50 20.0
25 100 10.0
50 200 5.0