Avago Technologies LSI53C320 - Manual (Page 23)

Ultra320 SCSI Functional Description 2-5
Version 2.2 Copyright © 2003 by LSI Logic Corporation. All rights reserved.
the valid data state. This method provides a minimum invalid data period
of four transfer periods.
Figure 2.2 provides a waveform diagram of paced data transfers and
illustrates the use of the P1 line.
Figure 2.2 Paced Transfer Example
The LSI53C320 uses the PPR negotiation that the SPI-4 draft standard
describes to establish a paced transfer agreement with the initiator on
the source bus and the target on the load bus.
Precompensation – When transmitting in the Ultra320 SCSI mode, the
LSI53C320 can use precompensation to adjust the strength of the REQ,
ACK, parity, and data signals. When a signal transitions to HIGH or LOW,
the LSI53C320 drives the signal at the signal drive strength for the first
data transfer period, and then lowers the signal drive strength on the
second data transfer period if the signal remains in the same state. The
LSI53C320 maintains the lower signal drive strength until the signal
again transitions HIGH or LOW.
Figure 2.3 illustrates the drivers
performance with precompensation enabled and disabled.
Invalid Data Valid Data Valid Data Invalid Data
REQ
ACK
P1
DATA