MSG

C/D

I/O

SCSI Phase

 

 

 

 

0

0

0

Data-Out

0

0

1

Data-In

0

1

0

Command

0

1

1

Status

1

0

0

Reserved

1

0

1

Reserved

1

1

0

Message-Out

1

1

1

Message-In

 

 

 

 

RARelative Addressing Mode23

When this bit is set, the 24-bit signed value in the DMA SCRIPTS Pointer Save (DSPS) register is used as a relative offset from the current DMA SCRIPTS Pointer (DSP) address (which is pointing to the next instruction, not the one currently executing). The relative mode does not apply to Return and Interrupt SCRIPTS.

Jump/Call an Absolute Address

Start execution at the new absolute address.

Command

Condition Codes

 

 

Absolute Alternate Address

Jump/Call a Relative Address

Start execution at the current address plus (or minus) the relative offset.

Command

Condition Codes

 

 

Don’t Care

Alternate Jump Offset

 

 

The SCRIPTS program counter is a 32-bit value pointing to the SCRIPTS instruction currently under execution by the LSI53C810A. The next address is formed by adding the 32-bit program counter to the 24-bit signed value of the last 24 bits of the Jump or Call instruction. Because it is signed (2’s complement), the jump can be forward or backward.

6-32

Instruction Set of the I/O Processor

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LSI 53C810A technical manual RARelative Addressing Mode23, Jump/Call an Absolute Address, Jump/Call a Relative Address