Seagate Ultra 160 사용자 설명서
Parallel SCSI Interface Product Manual, Rev. A )
25
Table 9:
SCSI Fast-160 and fast 320 non-compensatable timing budget in nanoseconds
Item
Fast-160
Fast-320
Comments
REQ(ACK) period
12.5
6.25
From Table 7
Transfer period
6.25
3.125
REQ(ACK) period / 2
Transmitter and receiver errors:
Total
Errors
Errors
Post
Compen
sation
Compen
sation
Total
Errors
Errors
Post
Compen
sation
Compen
sation
Worst case total of + and - time
shift except where noted
shift except where noted
Transmitter errors:
REQ(ACK) period tolerance / 2
0.06
0.06
0.06
0.06
Tolerance of transmitter plus mea-
surement error
surement error
b
Clock Jitter
0.25
0.25
0.25
0.50
System noise at transmitter
0.25
0.25
0.2
0.2
Time impact
Transmitter chip skew
0.75
0
0.75
0
Transmitter trace skew
0.2
0
0.2
0
Transmit time asymmetry
0.50
0.50
0.50
0
Compensated for on fast-320
SCSI devices
SCSI devices
Total transmitter error budget:
2.01
1.06
1.96
0.51
Receiver errors:
System noise at receiver
0.25
0.25
0.2
0.2
Time impact
Chip noise in receiver
0.2
0.2
0.2
0.2
Time impact
Receiver chip skew
0.75
0
0.75
0
Receiver trace skew
0.2
0
0.2
0
Receiver time asymmetry
0.35
0.35
0.35
0
Residual skew error
0
0.3
0
0.2
After skew compensation
Strobe offset tolerance
0
0.5
0
0.2
Accuracy of centering strobe
Offset induced time asymmetry
N/A
a
N/A
a
0.8
0.2
Time impact from cumulative D.C.
offsets at receiver
offsets at receiver
Receiver amplitude time skew
0.2
0.2
0.2
0.05
Total receiver error budget:
1.95
1.8
2.7
1.05
Total Transmitter + receiver error
budget:
budget:
3.96
2.86
4.44
1.53
Total timing error budget for
interconnect and system margin:
interconnect and system margin:
2.29
3.39
-1.535
1.565
Transfer period - (total transmitter
+ total receiver error budget)
a
Timing budgets in some previous standards neglected asymmetry & detection ambiguity and
lumps chip noise, clock jitter, crosstalk time shift, noise, ISI and receiver amplitude skew into
other terms (e.g., signal distortion skew) and/or ignores the effects.
b
other terms (e.g., signal distortion skew) and/or ignores the effects.
b
Tolerance adjusted for half cycle (i.e., transfer period)