Avago Technologies LSI53C876E User Manual
Page 117
SCSI Registers
4-23
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 LSI53C876 detects a higher priority
ID, the LSI53C876 deasserts BSY, deasserts its ID,
and waits until the next bus free state to try
arbitration again.
4.
The LSI53C876 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 LSI53C876 performs selection by asserting the
following onto the SCSI bus: SSEL/, the target’s ID
(stored in the
register),
and the LSI53C876 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
register, bit 2.
START
Start Sequence
5
When this bit is set, the LSI53C876 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
LSI53C876 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 LSI53C876 is not
connected to the SCSI bus.
WATN
Select with SATN/ on a Start Sequence
4
When this bit is set and the LSI53C876 SCSI function is
in initiator mode, the SATN/ signal is asserted during