Avago Technologies LSI53C876E - Manual (Page 217)

Transfer Control Instructions 5-27
5.6 Transfer Control Instructions
5.6.1 First Dword
IT[1:0] Instruction Type -
Transfer Control Instruction
[31:30]
OPC[2:0] OpCode [29:27]
This 3-bit field specifies the type of Transfer Control
Instruction to execute. All Transfer Control Instructions
can be conditional. They can be dependent on a
true/false comparison of the ALU Carry bit or a
comparison of the SCSI information transfer phase with
the Phase field, and/or a comparison of the First Byte
Received with the Data Compare field. Each instruction
can operate in Initiator or Target mode.
Jump Instruction
The LSI53C876 can do a true/false comparison of the
ALU carry bit, or compare the phase and/or data as
defined by the Phase Compare, Data Compare and
True/False bit fields.
If the comparisons are true, then it loads the DMA
SCRIPTS Pointer (DSP) register with the contents of the
DMA SCRIPTS Pointer Save (DSPS) register. The DSP
register now contains the address of the next instruction.
If the comparisons are false, the LSI53C876 fetches the
next instruction from the address pointed to by the
DMA
SCRIPTS Pointer (DSP) register, leaving the instruction
pointer unchanged.
OPC2 OPC1 OPC0 Instruction Defined
0 0 0 Jump
0 0 1 Call
0 1 0 Return
0 1 1 Interrupt
1 x x Reserved