4. The LSI53C810A repeats arbitration until it wins control of the SCSI bus. When it wins, the Won Arbitration bit is set in the SCSI Status Zero (SSTAT0) register, bit 2.

5. The LSI53C810A performs selection by asserting the following onto the SCSI bus: SSEL/, the target’s ID (stored in the SCSI Destination ID (SDID) register), and the LSI53C810A’s ID (stored in the SCSI Chip ID (SCID) 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 LSI53C810A 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 SCSI Control

 

One (SCNTL1) register, bit 4, indicates that the

 

 

LSI53C810A 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

 

SCSI Control One (SCNTL1) register to verify that the

 

 

LSI53C810A is not connected to the SCSI bus.

 

WATN Select with SATN/ on a Start Sequence4

When this bit is set and the LSI53C810A is in the initiator mode, the SATN/ signal is asserted during selection of a SCSI target device. This is to inform the target that the LSI53C810A has a message to send. If a selection time-out occurs while attempting to select a target device, SATN/ is deasserted at the same time SSEL/ is deasserted. When this bit is cleared, the SATN/ signal is not asserted during selection. When executing SCSI SCRIPTS, this bit is controlled by the SCRIPTS processor, but manual setting is possible in low level mode.

5-4

Operating Registers

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LSI 53C810A technical manual Watn Select with SATN/ on a Start Sequence4