Avago Technologies LSI53C896 User Manual
Page 134
4-22
Registers
Version 3.3
Copyright © 1998–2003 by LSI Logic Corporation. All rights reserved.
Full Arbitration, Selection/Reselection
1.The LSI53C896 SCSI function waits for a bus
free condition.
2.It asserts SBSY/ and its SCSI ID (the highest priority
ID stored in the
register) onto
the SCSI bus.
3.If the SSEL/ signal is asserted by another SCSI device
or if the LSI53C896 SCSI function detects a higher
priority ID, the LSI53C896 SCSI function deasserts
SBSY, deasserts its ID, and waits until the next bus
free state to try arbitration again.
4.The LSI53C896 SCSI function repeats arbitration until it
wins control of the SCSI bus. When it wins, the Won
Arbitration bit is set in the
register, bit 2.
5.The LSI53C896 SCSI function performs selection by
asserting the following onto the SCSI bus: SSEL/, the
target’s ID (stored in the
register), and the LSI53C896’s ID (stored in the
register).
6.After a selection is complete, the Function Complete bit
is set in the
SCSI Interrupt Status Zero (SIST0)
register, bit 6.
7.If a selection time-out occurs, the Selection Time-Out
bit is set in the
SCSI Interrupt Status One (SIST1)
register, bit 2.
START
Start Sequence
5
When this bit is set, the LSI53C896 starts the arbitration
sequence indicated by the Arbitration Mode bits. The
Start Sequence bit is accessed directly in low level mode.
During SCSI SCRIPTS operations, this bit is controlled by
the SCRIPTS processor. Do not start an arbitration
sequence if the connected (CON) bit in the
register, bit 4, indicates that
the LSI53C896 is already connected to the SCSI bus.
This bit is automatically cleared when the arbitration
sequence is complete. If a sequence is aborted, check bit
4 in the SCNTL1 register to verify that the LSI53C896 is
not connected to the SCSI bus.