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iAPX
432
Interface
Processor
Architecture
Reference
Manual
Canpleting
a
block
node
write
transfer
which
is
shorter
than
the
byte
count
is
a
two-step
process.
First,
the
AP
must
issue
an
ALTER
MAP
AND
SELECl'
DATA
SEGmNI'
function
with
the
entry
state
operand
to
"force
termination"
on window
o.
This
causes
the
IP
to
empty
its
FIFO
to
432 menory. Then,
the
AP
must
issue
an
additional
ALTER
MAP
AND
SELECI'
DATA
SEG1EN.I'
FUNcrICN
with
an
entry
state
operand
to
set
window 0
invalid
(close
the
window).
If
the
AP
attempts
to
close
a
block
mode
winda-t
without
first
-
forcing
termination,
the
IP
will
generate
a
fault,
interrupt
the
AP,
and
preserve
the
block
nOOe
window.
When
the
transfer
length
is
the
same
as
the
byte
count
attribute,
the
IP
autanatically
takes
care
of
the
last
block
which
will
be
short
if
the
transfer
size
is
not
a
multiple
of
eight.
BLOCK
moE
TERMINATICN
A
block
node
transfer
will
terminate
oormally
when
all
bytes
have
been
transferred,
or
it
may
terminate
prematurely
should
a
fault
occur.
In
both
cases,
the
IP
updates
the
transfer
status
attribute
and
issues
an
interrupt
request
to
notify
the
Attached
Processor.
Following
termination,
any
address
reference
falling
in
the
subrange
of
window 0
will
cause
the
windCM
to
fault
and
enter
the
error
state.
In
the
error
state,
requests
for
data
transfer
will
be
will
be
acknowledged
(negatively)
by
the
IP,
but
00
data
will
be
transferred.
This
prevents
a
DMA
controller,
for
example,
fran
continuing
to
transfer
data
after
a
fault
has
been det;.ected. The
faul
ted
wimow
cannot
be
re-used
until
it
is
closed
and
re-opened.
The
IP
tracks
the
progress
of
a
block
transfer
by
means
of
an
on-chip
byte
oounter.
The
IP
sets
this
counter
equal
to
the
byte
count
attribute
when
the
window
is
opened and decrements
it
with
each
byte
transferred.
When
the
on-chip
counter
underflows
(is
decremented
fran
zero)
all
bytes
have
been
transferred
and
the
operation
is
terminated
normally.
The
IP
will
terminate
a
block
transfer
prematurely
if
it
detects
a
fault
during
the
transfer.
In
addition,
the
I/O
controller
may
itself
force
termination
before
the
transfer
has
been
completed.
This
is
done
by
executing
an
ALTER
MAP
AND
SELECr
DATA
SEGMENT
function
with
the
transfer
status
attribute
set
to
"termination
forced."
Finally,
termination
may
be
forced
by
the
IP's
receipt
of
of
any
the
inter
processor
conmunication
messages "suspend and
fully
requalify
processor",
"close
windows",
or
"close
windows
am
enter
physical
node".
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