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7.6 Bus Phases
C156-E228-02EN 7-35
1) If (n×T1) ≥ (T2 + 700),
Average data transfer rate in SCSI = 1000/T1 (MB/s)
2) If (n×T1) > (T2 + 700),
Average data transfer rate in SCSI = (n×1000)/(T2 + 700) (MB/s)
where,
n: Value assigned to REQ/ACK Offset parameter
T1: Value in ns assigned to Transfer Period parameter (see Table 7.9)
T2: Average time in ns from REQi pulse transmission to corresponding ACKi
response at the pertinent pins of the SCSI connector on the ODD
Table 7.9 Parameters used for synchronous data transfer
Parameter Value Transter rate
REQ/ACK Offset 1 to 16
X '0C' (50 ns) Max. 20.0 MB/s*
1
X '12' (75 ns) Max. 13.3 MB/s*
1
X '19' (100 ns) Max. 10.0 MB/s*
1
X '25' (150 ns) Max. 6.6 MB/s*
1
X '32' (200 ns) Max. 5.0 MB/s*
1
X '3E' (250 ns) Max. 4.0 MB/s*
1
Transfer Period
(Minimum REQ Interval sent
from ODD)
(T1 in Figure 7.21)
X '4B' (300 ns) Max. 3.3 MB/s*
1
*1. If a single-ended SCSI bus is used, the maximum transfer rate must be
specified considering the bus configuration, the number of connected SCSI
devices, and transmission characteristics.
Figure 7.17 Data transfer rate in synchronous mode