Scsi control zero (scntl0), Register: 0x00 – Avago Technologies LSI53C896 User Manual
Page 133
SCSI Registers
4-21
Version 3.3
Copyright © 1998–2003 by LSI Logic Corporation. All rights reserved.
Register: 0x00
SCSI Control Zero (SCNTL0)
Read/Write
ARB[1:0]
Arbitration Mode Bits 1 and 0
[7:6]
Simple Arbitration
1.The LSI53C896 SCSI function waits for a bus free
condition to occur.
2.It asserts SBSY/ and its SCSI ID (contained in the
register) onto the SCSI bus. If
the SSEL/ signal is asserted by another SCSI
device, the LSI53C896 SCSI function deasserts
SBSY/, deasserts its ID and sets the Lost Arbitration
bit (bit 3) in the
register.
3.After an arbitration delay, the CPU should read the
register to check
whether a higher priority SCSI ID is present. If no
higher priority ID bit is set, and the Lost Arbitration
bit is not set, the LSI53C896 SCSI function
wins arbitration.
4.When the LSI53C896 SCSI function wins arbitration,
SSEL/ must be asserted using the
SCSI Output Control Latch (SOCL)
for a bus clear
plus a bus settle delay (1.2
µ
s) before a low level
selection is performed.
7
6
5
4
3
2
1
0
ARB[1:0]
START
WATN
EPC
R
AAP
TRG
1
1
0
0
0
x
0
0
ARB1
ARB0 Arbitration Mode
0
0
Simple arbitration
0
1
Reserved
1
0
Reserved
1
1
Full arbitration, selection/reselection