clear the ID Mode bit or any of the PCI configuration registers. This bit is not self-clearing; it must be cleared to clear the reset condition (a hardware reset also clears this bit).

SIGP

Signal Process

5

 

SIGP is a R/W bit that is writable at any time, and polled

 

and reset using Chip Test Two (CTEST2). The SIGP bit

 

is used in various ways to pass a flag to or from a running

 

SCRIPTS instruction.

 

 

The only SCRIPTS instruction directly affected by the

 

 

SIGP bit is Wait for Selection/Reselection. Setting this bit

 

causes that instruction to jump to the alternate address

 

immediately. The instructions at the alternate jump

 

 

address should check the status of SIGP to determine

 

 

the cause of the jump. The SIGP bit is usable at any time

 

and is not restricted to the wait for selection/reselection

 

condition.

 

SEM

Semaphore

4

 

The SCRIPTS processor may set this bit using a

 

 

SCRIPTS register write instruction. An external processor

 

may also set it while the LSI53C875A is executing a

 

 

SCRIPTS operation. This bit enables the LSI53C875A to

 

notify an external processor of a predefined condition

 

 

while SCRIPTS are running. The external processor may

 

also notify the LSI53C875A of a predefined condition and

 

the SCRIPTS processor may take action while SCRIPTS

 

are executing.

 

CON

Connected

3

 

This bit is automatically set any time the LSI53C875A is

 

connected to the SCSI bus as an initiator or as a target.

 

It is set after successfully completing selection or when

 

 

the LSI53C875A responds to a bus-initiated selection or

 

reselection. It is also set after the LSI53C875A wins

 

 

arbitration when operating in low level mode. When this

 

bit is clear, the LSI53C875A is not connected to the SCSI

 

bus.

 

INTF

Interrupt-on-the-Fly

2

 

This bit is asserted by an INTFLY instruction during

 

 

SCRIPTS execution. SCRIPTS programs do not halt

 

when the interrupt occurs. This bit can be used to notify a service routine, running on the main processor while

SCSI Registers

4-49

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Image 141
LSI 53C875A technical manual Sigp, Signal Process, Semaphore, Intf