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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.
9.5.1
Synchronous data transfer periods supported
Table 10 lists synchronous data transfer periods supported by the drive.
Table 10:
Synchronous data transfer periods supported
M (Decimal)
Transfer period (M times 4 nanoseconds)
12 [1]
15 [1]
18 [1]
25
31
37
50
62
75
87
100
[1]
Fast-20 (Ultra SCSI) transfer rates.
9.5.2
REQ/ACK offset
The maximum REQ/ACK value supported by Elite 23 SCSI drives is 15 (0Fh).
9.6
Physical interface
Figures 12 and 13 show the locations of the drive physical interface components. The locations of the DC
power connector, the SCSI interface connector, and the drive select and option select headers are shown.
Details of the physical, electrical and logical characteristics are given in sections following, while the SCSI
operational aspects of Seagate drive interfaces are provided in the SCSI Interface Product Manual, part num-
ber 77738479.
This section describes the connectors, cables, signals, terminators and bus timing of the DC and SCSI I/O
interface. See Sections 9.8 and 9.9 for additional terminator information.
9.6.1
DC cable and connector
The drive receives DC power through a 4-pin connector (see Figure 12 for pin assignments) mounted at the
rear of the main PCB. Recommended part numbers of the mating DC power connector are listed below, but
equivalent parts may be used.
Type of Cable
Connector
14 AWG
AMP 1-480424-0
Transfer rate (mega transfers/second)
50 [1]
62.5 [1]
75 [1]
100
125
150
200
250
300
350
400
Contacts (20-14 AWG)
AMP 60619-4 (loose piece)
AMP 61117-4 (strip)
Elite 23 Product Manual, Rev. A
20.0 [1]
16.0 [1]
13.33 [1]
10.0
8.0
6.66
5.0
4.0
3.33
2.86
2.5
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