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48
9.5
Synchronous data transfer
9.5.1
Synchronous data transfer periods supported
Table 11 and Section 9.5.2 list synchronous data transfer periods supported by the drive. 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, P/N
77738479.
Table 11:
Synchronous data transfer periods for drive
Transfer period
M (Decimal)
(M times 4 nanoseconds)
12 [1]
50 [1]
15 [1]
62.5 [1]
18 [1]
75 [1]
25
100
31
125
37
150
50
200
62
250
75
300
87
350
100
400
[1]
FAST-20 SCSI transfer periods
9.5.2
REQ/ACK offset
The maximum value supported by the Cheetah 4LP family drives for REQ/ACK offset is 15 (0Fh).
9.6
Physical interface
Figure 13 shows the locations of the drive physical interface components for the "N" drives. Shown are the
locations of the DC power connector, the SCSI interface connector, the I/O line terminators, and the drive
select 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, P/N
77738479.
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.
9.6.1
DC cable and connector
With the exception of the "WC" and "DC" drives, the drive receives DC power through a 4 pin connector (see
Figure 13 for pin assignment) mounted at the rear of the main PCB. Recommended part numbers of the mat-
ing connector are listed below, but equivalent parts may be used.
Type of cable
Connector
14 AWG
MP 1-480424-0
Models "WC" and "DC" receive power through the 80 pin I/O connector. See Tables 13d and 13e.
Transfer rate
(mega transfers/second)
20.0
16.0
13.33
10.0
8.0
6.66
5.00
4.00
3.33
2.86
2.5
Contacts (20-14 AWG)
AMP 60619-4 (Loose Piece)
AMP 61117-4 (Strip)
Cheetah 4LP Product Manual, Rev. B
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