Table Relative

Treats the alternate jump address as a relative jump and fetches the device ID, synchronous offset, and synchronous period indirectly. The value in bits [23:0] of the first four bytes of the SCRIPTS instruction is added to the data structure base address to form the fetch address.

 

Command

 

Table Offset

 

 

 

 

 

 

 

Absolute Jump Offset

 

 

 

 

 

 

Sel

Select with ATN/

 

24

 

This bit specifies whether SATN/ is asserted during the

 

selection phase when the LSI53C875A is executing a

 

Select instruction. When operating in Initiator mode, set

 

this bit for the Select instruction. If this bit is set on any

 

other I/O instruction, an illegal instruction interrupt is

 

generated.

 

 

R

Reserved

 

[23:20]

ENDID[3:0]

Encoded SCSI Destination ID

[19:16]

 

This 4-bit field specifies the destination SCSI ID for an I/O

 

instruction.

 

 

R

Reserved

 

[15:11]

CC

Set/Clear Carry

 

10

 

This bit is used in conjunction with a Set or Clear

 

instruction to set or clear the Carry bit. Setting this bit

 

with a Set instruction asserts the Carry bit in the ALU.

 

Clearing this bit with a Clear instruction deasserts the

 

Carry bit in the ALU.

 

 

TM

Set/Clear Target Mode

 

9

This bit is used in conjunction with a Set or Clear instruction to set or clear Target mode. Setting this bit with a Set instruction configures the LSI53C875A as a Target device (this sets bit 0 of the SCSI Control Zero (SCNTL0) register). Clearing this bit with a Clear instruction configures the LSI53C875A as an Initiator device (this clears bit 0 of the SCNTL0 register).

5-20

SCSI SCRIPTS Instruction Set

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LSI 53C875A technical manual Table Relative, Command Table Offset Absolute Jump Offset