Avago Technologies LSI8751D - Manual (Page 212)

6-16 Instruction Set of the I/O Processor
Initiator Mode
Select Instruction
The LSI53C875 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.
If the LSI53C875 wins arbitration, it attempts to select the
SCSI device whose ID is defined in the destination ID
field of the instruction. Once the LSI53C875 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.
If the LSI53C875 is selected or reselected before winning
arbitration, 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
LSI53C875 to Initiator mode if it is reselected, or to Tar-
get 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 LSI53C875 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
LSI53C875 receives a Disconnect Message or a
Command Complete Message.
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