3.The LSI53C810A compares the SCSI phase bits in the DMA Command (DCMD) register with the latched SCSI phase lines stored in the SCSI Status One (SSTAT1) register. These phase lines are latched when SREQ/ is asserted.

4.If the SCSI phase bits match the value stored in the SCSI SCSI Status One (SSTAT1) register, the LSI53C810A transfers the number of bytes specified in the DMA Byte Counter (DBC) register starting at the address pointed to by the DMA Next Address (DNAD) register.

5.If the SCSI phase bits do not match the value stored in the SCSI Status One (SSTAT1) register, the LSI53C810A generates a phase mismatch interrupt and the instruction is not executed.

6.During a Message-Out phase, after the LSI53C810A has performed a select with Attention (or SATN/ is manually asserted with a Set ATN instruction), the LSI53C810A deasserts SATN/ during the final SREQ/SACK/ handshake of the first move of Message-Out bytes after SATN/ was set.

7.When the LSI53C810A is performing a block move for Message-In phase, it does not deassert the SACK/ signal for the last SREQ/SACK/ handshake. Clear the SACK/ signal using the Clear SACK I/O instruction.

SCSIP[2:0] SCSI Phase[26:24]

This 3-bit field defines the desired SCSI information transfer phase. When the LSI53C810A operates in Initiator mode, these bits are compared with the latched SCSI phase bits in the SCSI Status One (SSTAT1) register. When the LSI53C810A operates in Target mode, the LSI53C810A asserts the phase defined in this field. The following table describes the possible combinations and the corresponding SCSI phase.

Block Move Instructions

6-11

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LSI 53C810A technical manual SCSIP20 Scsi Phase2624