Avago Technologies LSI53C1020 - Manual (Page 46)

2-20 Functional Description
Version 2.4 Copyright © 2001–2004 by LSI Logic Corporation. All rights reserved.
Precompensation – When transmitting in the Ultra320 SCSI mode, the
LSI53C1020 uses precompensation to adjust the strength of the REQ,
ACK, parity, and data signals. When a signal transitions to HIGH or LOW,
the LSI53C1020 boosts 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 LSI53C1020
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.
Figure 2.3 Example of Precompensation
2.4.1.4 Packetized Transfers
Packetized transfers are also referred to as information unit transfers.
They reduce overhead on the SCSI bus by merging several of the SCSI
bus phases. Packetized transfers can only occur in DT Data phases. The
initiator and target must establish either a DT synchronous transfer
Normal Drive Strength
Boosted Drive Strength Normal Drive Strength
a. Drivers with Precompensation Disabled
b. Drivers with Precompensation Enabled