LSI LSI53C1000, Technical Manual

Page: 185 / 384

SCSI Registers 4-75
Register: 0x43
SCSI Interrupt Status One (SIST1)
Read Only
Reading the SIST1 register returns the status of the various interrupt
conditions, whether they are enabled in the
SCSI Interrupt Enable One
(SIEN1) register or not. Each bit set indicates an occurrence of the
corresponding condition. Reading the SIST1 clears the interrupt
condition.
R Reserved [7:5]
SBMC SCSI Bus Mode Change 4
This bit is set when the DIFFSENS pin detects a change
in voltage level indicating the SCSI bus has switched
between SE, LVD, or HVD modes. HVD is not supported.
R Reserved 3
STO Selection or Reselection Time-Out 2
This bit is set when the SCSI device which the
LSI53C1000 is attempting to select or reselect does not
respond within the programmed time-out period. See the
description of the
SCSI Timer Zero (STIME0) register,
bits [3:0], for more information on the time-out timer.
GEN General Purpose Timer Expired 1
This bit is set when the general purpose timer expires.
The time measured is the time between enabling and
disabling of the timer. See the description of the
SCSI
Timer One (STIME1) register, bits [3:0], for more
information on the general purpose timer.
HTH Handshake-to-Handshake Timer Expired 0
This bit is set when the handshake-to-handshake timer
expires. The time measured is the SCSI Request-to-
Request (target) or Acknowledge-to-Acknowledge
(initiator) period. See the description of the
SCSI Timer
Zero (STIME0) register, bits [7:4], for more information on
the handshake-to-handshake timer.
7 5 4 3 2 1 0
R SBMC R STO GEN HTH
0 0 0 0 0 0 0 0