Avago Technologies LSI53C825AE - Manual (Page 198)

5-14 SCSI SCRIPTS Instruction Set
5.4 I/O Instruction
I/O Instructions perform the following SCSI operations in Target and
Initiator mode. These I/O operations are chosen with the opcode bits in
the
DMA Command (DCMD) register.
This section describes these I/O operations.
5.4.1 First Dword
IT[1:0] Instruction Type - I/O Instruction [31:30]
The IT bit configuration (01) defines an I/O Instruction
Type.
OPC[2:0] Opcode [29:27]
The Opcode bit configurations define the I/O operation
performed, but the Opcode bit meanings change in
Target mode compared to Initiator mode. Opcode bit
configurations (101, 110, and 111) are considered
Read/Write instructions, and are described in
Section 5.5, “Read/Write Instructions.” This section
describes Target mode operations.
OPC2 OPC1 OPC0 Target Mode Initiator Mode
0 0 0 Reselect Select
0 0 1 Disconnect Wait Disconnect
0 1 0 Wait Select Wait Reselect
0 1 1 Set Set
1 0 0 Clear Clear