53
Chapter 7 SCSI Interface
Table 7.2.1.3 : Extended Message Code
MODIFY DATA POINTER: Not supported.
SYNCHRONOUS DATA TRANSFER REQUEST determines the format of
the parameter for synchronous data transfers. The values are shown in the
following table.
Table 7.2.1.4 : SYNCHRONOUS DATA TRANSFER REQUEST Message Format
TRANSFER PERIOD FACTOR determines the transfer speed of synchronous
transfers. The values are as shown in the following table.
Table 7.2.1.5 : Transfer Period Factor Code
REQ/ACK Offset is set to the maximum offset in synchronous transfers.
When REQ/ACK Offset is 0 transfers are asynchronous.
Code
Extended Message
00h
MODIFY DATA POINTER
01h
SYNCHRONUS DATA TRANSFER REQUEST
02h
Reserved
03h
WIDE DATA TRANSFER REQUEST
04h
PARALLEL PROTOCOL REQUEST
05-ffh
Reserved
Bit
Byte
7
6
5
4
3
2
1
0
0
Extended Message(01h)
1
Extended Message Length(03h)
2
SYNCHROUS DATA POINTER(01h)
3
TRANSFER PERIOD FACTOR
4
REQ/ACK Offset
Code
Description
00-08h
Reserved
09h
Transfer Period = 12.5ns (FAST-80)
0Ah
Transfer Period = 25ns (FAST-40)
0Bh
Transfer Period = 30.3ns (FAST-40)
0Ch
Transfer Period = 50ns (FAST-20)
0D-18h
Transfer Period = Transfer factor * 4ns (FAST-20)
19-31h
Transfer Period = Transfer factor * 4ns (FAST-10)
32-ffh
Transfer Period = Transfer factor * 4ns (FAST-5)