the LSI53C875A to Initiator mode if it is reselected, or to Target mode if it is selected.

If the Select with SATN/ field is set, the SATN/ signal is asserted during the selection phase.

Wait Disconnect Instruction

The LSI53C875A waits for the Target to perform a “legal” disconnect from the SCSI bus. A “legal” disconnect occurs when SBSY/ and SSEL/ are inactive for a minimum of one Bus Free delay (400 ns), after the LSI53C875A receives a Disconnect Message or a Command Complete Message.

Wait Reselect Instruction

If the LSI53C875A is selected before being reselected, it fetches the next instruction from the address pointed to by the 32-bit jump address field stored in the DMA Next Address (DNAD) register. Manually set the LSI53C875A to Target mode when it is selected.

If the LSI53C875A is reselected, it fetches the next instruction from the address pointed to by the DMA SCRIPTS Pointer (DSP) register.

If the CPU sets the SIGP bit in the Interrupt Status Zero (ISTAT0) register, the LSI53C875A aborts the Wait Reselect instruction and fetches the next instruction from the address pointed to by the 32-bit jump address field stored in the DMA Next Address (DNAD) register.

Set Instruction

When the SACK/ or SATN/ bits are set, the corresponding bits in the SCSI Output Control Latch (SOCL) register are set. When the target bit is set, the corresponding bit in the SCSI Control Zero (SCNTL0) register is also set. When the carry bit is set, the corresponding bit in the ALU is set.

Clear Instruction

When the SACK/ or SATN/ bits are cleared, the corresponding bits are cleared in the SCSI Output Con- trol Latch (SOCL) register. 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.

I/O Instruction

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LSI 53C875A technical manual Wait Disconnect Instruction, Wait Reselect Instruction