Seagate Ultra 320 - Manual (Page 50)

36 Parallel SCSI Interface Product Manual, Rev. A )
Figure 7. DT synchronous transfer example
Figure 8. Paced transfer example
2.8 Paced transfer on a SCSI bus
A SCSI bus that supports paced transfers has additional driver and receiver functions required over those used
with synchronous transfers or asynchronous transfers. These functions include driver precompensation,
receiver skew compensation, receiver clock shifting, and an optional receiver signal adjustment. In addition,
the drive precompensation may be switched out of the data path at the request of the receiving SCSI device.
REQ or ACK
DT Data
DT
Clock
DT
Clock
DT
Clock
DT
Clock
transfer period = 25 ns
25 ns 25 ns 25 ns
Example: A negotiated transfer period of 25 ns equates to
a transfer rate of 40 megatransfers per second.
REQ or ACK
DT Data
DT
Clock
DT
Clock
DT
Clock
DT
Clock
transfer period = 6.25 ns
6.25 ns 6.25 ns 6.25 ns
Example: A negotiated transfer period of 6.25 ns equates to
a transfer rate of 160 megatransfers per second.