Barracuda 18XL Product Manual, Rev. A 61
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 “Extended Message” on message protocol in the SCSI Interface Product
Manual, part number 75789509. Byte 3 of the message format lists a transfer period factor. The factors possi-
ble and equivalent transfer periods are listed in Table 11.
Table 11: Synchronous data transfer periods for drive
Notes.
[1] Faster timings may be allowed by future SCSI parallel interface standards.
[2] Fast-40 data transfer rates that have a period equal to 25 ns or 30.3 ns.
[3] Fast-20 data transfer rates that have a period of
≤
96 ns and
≥
50 ns.
[4] Fast-10 data transfer rates that have a period of
≤
196 ns and
≥
100 ns.
[5] Fast-5 data transfer rates that have a period of
≤
1020 ns and
≥
200 ns.
[6] Fast-80 data transfer rates that have a period equal to 12.5 ns.
9.5.2 REQ/ACK offset
The maximum value supported by the Barracuda 18XL family drives for REQ/ACK offset is 15 (0Fh).
9.6 Physical interface
Figures 9a and 9b show the locations of the drive physical interface components for the various models of the
drive. Shown are the locations of the DC power connector, the SCSI interface connector, 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, part number
75789509.
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 “LC” drives, the drive receives DC power through a 4 pin connector (see Figure 9a for
pin assignment) mounted at the rear of the main PCBA. Recommended part numbers of the mating connector
are listed below, but equivalent parts may be used.
Model “LC” receives power through the 80 pin I/O connector. See Table 13d.
Transfer period
factor
Transfer period
(nanoseconds)
00h-09h Reserved [1]
0Ah Transfer period equals 25 ns [2]
0Bh Transfer period equals 30.3 ns [2]
0Ch Transfer period equals 50 ns [3]
0Dh-18h Transfer period equals the transfer period factor * 4 [3]
19h-31h Transfer period equals the transfer period factor * 4 [4]
32h-FFh Transfer period equals the transfer period factor * 4 [5]
05h Transfer period equals 12.5 ns [6]
Type of cable Connector Contacts (20-14 AWG)
14 AWG MP 1-480424-0 AMP 60619-4 (Loose Piece)
AMP 61117-4 (Strip)
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