LSI Symbios SYM53C040, Technical Manual

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SCSI Core Operation 2-7
Figure 2.3 Initiating Arbitration and Selection/Reselection
Reset SEL/ and
Assert Data Bus
(0xFC01 Bits 2, 0)
Write ID Bit to
(Reg. 0xFC00)
Output Data Register
Set ARB
(0xFC02 Bit 0)
Set AS_LVD
(0xFC02 Bit 7)***
Check
Arb. In Prog. Bit
(0xFC01 Bit 6)
Wait 2.2 s
Arbitration Delay
Check
Lost Arb. Bit
(0xFC01 Bit 5)
Read 0xFC00 to See
If a Higher Priority ID
Is Present
Higher
Priority ID
Present
?
No
Yes
0
1
0
1
A
Check
Lost Arb. Bit
(0xFC01 Bit 5)
0
1
A
B
B
Set Assert SEL/ Bit
(0xFC01 Bit 2)
Wait 1.2
µ
s Min.
(Bus Clear + Settle)
Set Target Mode Bit
(0xFC02 Bit 6)*
Set TE
(0xFC03 Bit 1)***
Set Assert I_O/ Bit
(0xFC03 Bit 0)*
Write Target and
Initiator’s ID Bits
to Output Reg.
(Reg. 0xFC00)
Assert BSY/ and
Assert Data Bus
(0xFC01 Bits 3, 0)
Reset ARB Bit
(0xFC02 Bit 0)
C
Selection/
Reselection
Complete?
No
C
Reset Assert BSY/
Bit (0xFC01 Bit 3)
Yes
Reset the Select
Enable Register
(Reg. 0xFC04)
BSY/
Asserted within
250 ms
No
Yes
Selection
Time-out
?
Set Assert BSY/
(0xFC01 Bit 3)*
Reset AS_LVD
(0xFC02 Bit 7)***
Information Transfer Phases
* Reselection Only
** Poll Interrupt
Request Active Bit or
wait for interrupt
*** LVD operation only
Reset ARB
(0xFC02 Bit 0)
Reset SEL
(0xFC01 Bit 2)
**