Clear Instruction

When the SACK/ or SATN/ bits are cleared, the corresponding bits are cleared in the SCSI Output Con- trol Latch (SOCL) register. Do not set SACK/ or SATN/ except for testing purposes. When the target bit is cleared, the corresponding bit in the SCSI Control Zero (SCNTL0) register is cleared. When the carry bit is cleared, the corresponding bit in the ALU is cleared.

Note: None of the signals are cleared on the SCSI bus in Target mode.

Initiator Mode

OPC2

OPC1

OPC0

Instruction Defined

 

 

 

 

0

0

0

Select

0

0

1

Wait Disconnect

0

1

0

Wait Reselect

0

1

1

Set

1

0

0

Clear

 

 

 

 

Select Instruction

1.The LSI53C810A arbitrates for the SCSI bus by asserting the SCSI ID stored in the SCSI Chip ID (SCID) register. If it loses arbitration, it tries again during the next available arbitration cycle without reporting any lost arbitration status.

2.If the LSI53C810A wins arbitration, it attempts to select the SCSI device whose ID is defined in the destination ID field of the instruction. Once the LSI53C810A wins arbitration, it fetches the next instruction from the address pointed to by the DMA SCRIPTS Pointer (DSP) register. This way the SCRIPTS can move to the next instruction before the selection completes. It continues executing SCRIPTS until a SCRIPT that requires a response from the Target is encountered.

3.If the LSI53C810A is selected or reselected before winning arbitration, it fetches the next instruction from the address pointed to by the 32-bit jump address

I/O Instruction

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LSI 53C810A technical manual Clear Instruction, Select Instruction