SCSI Functional Description
2-49
When the LSI53C1000 is operating in the Initiator mode, Interrupt-on-the-
Fly, Function Complete (CMP), Selected (SEL), Reselected (RSL),
General Purpose Timer Expired (GEN), and Handshake-to-Handshake
Timer Expired (HTH) interrupts are nonfatal.
When operating in the Target mode, Interrupt-on-the-Fly, SATN/ active
(M/A), CMP, SEL, RSL, GEN, and HTH are nonfatal. Refer to the
description for the Disable Halt on a Parity/CRC/AIP Error or SATN/
active (Target Mode Only) bit, DHP, in the
register to configure the chip’s behavior when the SATN/ interrupt is
enabled during Target mode operation.
The reason for nonfatal interrupts is to prevent the SCRIPTS from
stopping when an interrupt occurs that does not require service from the
CPU. This prevents an interrupt when arbitration is complete (CMP set),
when the LSI53C1000 is selected or reselected (SEL or RSL set), when
the initiator asserts ATN (target mode: SATN/ active), or when the
General Purpose or Handshake-to-Handshake timers expire. These
interrupts are not needed for events that occur during high level
SCRIPTS operation.
2.2.16.4 Masking
Masking an interrupt means disabling or ignoring that interrupt. Clearing
bits in the
SCSI Interrupt Enable Zero (SIEN0)
and
registers will mask SCSI interrupts. Clearing bits in the
register will mask DMA interrupts. Masking
an interrupt after INTA/ is asserted does not cause INTA/ to be negated.
How the chip responds to masked interrupts depends on: whether polling
or hardware interrupts are being used; whether the interrupt is fatal or
nonfatal; and whether the chip is operating in the Initiator or Target mode.
If a nonfatal interrupt occurs while masked, SCRIPTS continues. The
appropriate bit in the
SCSI Interrupt Status Zero (SIST0)
or
is still set, the SIP bit in the
is not set, and the INTA/ pin is not asserted.
If a fatal interrupt occurs while masked, SCRIPTS halts. The appropriate
bit in the
SCSI Interrupt Status Zero (SIST0)
, or
SCSI Interrupt Status One (SIST1)
register is set, the SIP or DIP bit in
the
Interrupt Status Zero (ISTAT0)
register is set, but the INTA/ pin is not
asserted.
Содержание LSI53C1000
Страница 6: ...vi Preface...
Страница 16: ...xvi Contents...
Страница 28: ...1 12 Introduction...
Страница 234: ...4 124 Registers...
Страница 314: ...6 40 Specifications This page intentionally left blank...
Страница 318: ...6 44 Specifications This page intentionally left blank...
Страница 344: ...6 70 Specifications This page intentionally left blank...
Страница 350: ...6 76 Specifications Figure 6 42 LSI53C1000 329 Ball Grid Array Bottom view...
Страница 352: ...6 78 Specifications...
Страница 360: ...A 8 Register Summary...
Страница 376: ...IX 12 Index...