2-24
Functional Description
2.2.5.2 Parallel Protocol Request
CRC, Sync/Wide, DT, Quick Arbitration and Selection (QAS), and
“information units” are negotiated with a new SCSI extended message:
Transfer Period Factor (Byte 3) – Transfer Period Factor is the old
Synchronous Period value. These are the same with one addition for the
80 megatransfers/s rate:
The transfer period depends on the data transfer speed, NOT the clock
period. So, in DT mode, 0x09 means 12.5 ns between clock edges which
really means a 25 ns clock period. In DT mode, 0x0A would mean a
clock period of 50 ns but a data rate of 40 megatransfers/s (25 ns). In
ST mode, 0x0A would mean a clock period of 25 ns and a data rate of
40 megatransfers/s.
Req/Ack Offset (Byte 5) – Req/Ack Offset is the maximum SCSI offset.
Transfer Width Exponent (Byte 6) – Transfer Width Exponent is the
old width value. It is set to 0 (8-bit SCSI width) or 1 (16-bit SCSI width).
Byte 0
0x01
Extended message
Byte 1
0x06
Length
Byte 2
0x04
Parallel Protocol Request (PPR)
Byte 3
0xXX
Transfer Period Factor
Byte 4
0x00
Reserved
Byte 5
0xXX
Req/Ack Offset
Byte 6
0xXX
Transfer Width Exponent
Byte 7
0x0X
Protocol options
0x09
=
12.5 ns (Ultra160 SCSI) only valid when using DT
0x0A
=
25 ns (Ultra2 SCSI)
0x0B
=
30.3 ns
0x0C
=
50 ns (Ultra SCSI)
0x0D–0xFF
=
(in ns)
value
4
×
Period
=
Содержание LSI53C1000
Страница 6: ...vi Preface...
Страница 16: ...xvi Contents...
Страница 28: ...1 12 Introduction...
Страница 234: ...4 124 Registers...
Страница 314: ...6 40 Specifications This page intentionally left blank...
Страница 318: ...6 44 Specifications This page intentionally left blank...
Страница 344: ...6 70 Specifications This page intentionally left blank...
Страница 350: ...6 76 Specifications Figure 6 42 LSI53C1000 329 Ball Grid Array Bottom view...
Страница 352: ...6 78 Specifications...
Страница 360: ...A 8 Register Summary...
Страница 376: ...IX 12 Index...