TEST
CAPABILITIES
For more information
on
how
to write routines to test the TLB, refer to the
80386 Programmer's Reference Manual.
12.2
BOARD-LEVEL TESTS
For board-level testing, it
is
often desirable to isolate areas of the board from the interactions
of
other devices. The 80386 can be forced to a state in which all but two of its pins are
effectively removed from their circuits. This state
is
accomplished through the HOLD and
HLDA
pins.
When the
HOLD input of the 80386
is
asserted, the 80386 places all of its outputs except
for HLDA in the three-state condition. HLDA
is
then driven high. The 80386 remains in
this condition until
HOLD
is
de-asserted. Note that RESET being asserted takes priority
over
HOLD requests.
The
80386 completes its current bus cycle before responding to the HOLD input. Detailed
information
on
HOLD
jHLDA
response
is
given
in
Chapter
3.
12-5
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