AMD-K6-2E Datasheet, PDF (130/332 Pages) Advanced Micro Devices – AMD-K6™-2E Embedded Processor

AMD-K6™-2E Processor Data Sheet
Preliminary Information
22529B/0—January 2000
5.33
LOCK# (Bus Lock)
Pin Attribute
Output
Pin Location
Summary
AH-04
The processor asserts LOCK# during a sequence of bus cycles to
ensure that the cycles are completed without allowing other bus
masters to intervene. Locked operations consist of two to five
bus cycles. LOCK# is asserted during the following operations:
s An interrupt acknowledge sequence
s Descriptor Table accesses
s Page Directory and Page Table accesses
s XCHG instruction
s An instruction with an allowable LOCK prefix
In order to ensure that locked operations appear on the bus and
are visible to the entire system, any data operands addressed
during a locked cycle that reside in the processor’s cache are
flushed and invalidated from the cache prior to the locked
operation. If the cache line is in the modified state, it is written
back and invalidated prior to the locked operation. Likewise,
any data read during a locked operation is not cached.
The processor is designed so that LOCK# does not glitch.
Driven and Floated
During a locked cycle, LOCK# is asserted off the same clock
edge on which ADS# is asserted and remains asserted until the
last BRDY# of the last bus cycle is sampled asserted. The
processor negates LOCK# for at least one clock between
consecutive sequences of locked operations to allow the system
logic to arbitrate for the bus.
LOCK# is floated off the clock edge on which BOFF# is sampled
asserted and off the clock edge on which the processor asserts
HLDA in response to HOLD. When LOCK# is floated due to
BOFF# sampled asserted, the system logic is responsible for
preserving the lock condition while LOCK# is in the
high-impedance state.
112
Signal Descriptions
Chapter 5