Synchronous Data Transfer; Synchronous Data Transfer Periods Supported; Req/Ack Offset; Physical Interface - Seagate ST3300655LW Product Manual

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 Parallel SCSI Interface
Manual and SCSI Commands Reference Manual.
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 14 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 14: Synchronous DT DATA transfer periods
Transfer period
M (decimal) (nanoseconds)
8 6.25
9 12.5
10 25
12 50
25 100
Table 15 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.
Table 15: Synchronous ST DATA transfer periods
Transfer period
M (decimal) (nanoseconds)
10 25
12 50
25 100
50 200
1. This transfer rate is only allowed when using the LVD interface.
9.5.2

REQ/ACK offset

Cheetah 15K.5 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 13 and 14 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 Parallel SCSI Interface Manual.
58
Transfer rate
(megatransfers/second)
160.0
80.0
40.0
20.0
10.0
Transfer rate
(megatransfers/second)
1
40.0
20.0
10.0
5.0
Transfer rate
(MBytes/second) on wide bus
320.0
160.0
80.0
40.0
20.0
Cheetah 15K.5 SCSI Product Manual, Rev. D