5 transfer period factor – Seagate Ultra 320 User Manual
Page 57
Parallel SCSI Interface Product Manual, Rev. A )
43
2.12.5
Transfer period factor
The Transfer Period Factor field selects the transfer period and determines which transfer rate’s timing values
in Tables 5, 6, 7, and 8 shall be honored, provided that REQ/ACK OFFSET is greater than 00h. The field val-
ues are defined in Table 14.
Table 15 shows which transfer period factors may be used with different types of transfer agreements, provided
REQ/ACK OFFSET is greater than 00h.
Table abbreviations are defined as follows:
M =
Mandatory: Support for the indicated transfer agreement shall be implemented if the indicated transfer
period factor is implemented.
O =
Optional: Support for the indicated transfer agreement may be implemented if the indicated transfer
period factor is implemented.
NS = Not Supported: The indicated transfer agreement shall not be allowed if the indicated transfer factor is
selected.
Table 20 defines valid combinations of TRANSFER PERIOD FACTOR and other fields.
Table 14:
Transfer period factor
Value
Description
Message
Transfer rate
00h - 06h
Reserved
N/A
N/A
07h
Transfer period equals 3.125 ns
PPR
Fast-320
08h
Transfer period equals 6.25 ns
PPR
Fast-160
09h
Transfer period equals 12.5 ns
PPR
Fast-80
0Ah
Transfer period equals 25 ns
PPR, SDTR
Fast-40
0Bh
Transfer period equals 30.3 ns
PPR, SDTR
Fast-40
0Ch
Transfer period equals 50 ns
PPR, SDTR
Fast-20
0Dh - 18h
Transfer period equals the TRANSFER PERIOD FACTOR x 4
PPR, SDTR
Fast-20
19h - 31h
Transfer period equals the TRANSFER PERIOD FACTOR x 4
PPR, SDTR
Fast-10
32h - FFh
Transfer period equals the TRANSFER PERIOD FACTOR x 4
PPR, SDTR
Fast-5
Table 15:
Transfer period factor relationships
Value
Transfer agreement
Synchronous
Paced
Data group
Information
unit
ST data
DT data
00h - 06h
Reserved
07h - 08h
NS
M
NS
M
NS
M
09h
M
NS
O
O
NS
M
0Ah
M
NS
O
O
O
O
0Bh
M
NS
O
O
O
O
0Ch
M
NS
O
O
O
O
0Dh - 18h
M
NS
O
O
O
O
19h - 31h
M
NS
O
O
O
O
32h - FFh
M
NS
O
O
O
O