Avago Technologies LSI53C876E - Manual (Page 145)

SCSI Registers 4-51
SRST Software Reset 6
Setting this bit resets the LSI53C876 SCSI function. All
operating registers are cleared to their respective default
values and all SCSI signals are deasserted. Setting this
bit does not assert the SCSI RST/ signal. This reset does
not 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 LSI53C876 SCSI function is
executing a SCRIPTS operation. This bit enables the
SCSI function to notify an external processor of a
predefined condition while SCRIPTS are running. The
external processor may also notify the LSI53C876 SCSI
function 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 LSI53C876
SCSI function is connected to the SCSI bus as an initiator
or as a target. It is set after successfully completing
selection or when the LSI53C876 SCSI function responds
to a bus-initiated selection or reselection. It is also set
after the SCSI function wins arbitration when operating in
low level mode. When this bit is clear, the LSI53C876
SCSI function is not connected to the SCSI bus.