Filter
Top Products
FUNcrIONS
4-
3.
FUNcrICN
EXOCUTICN
The
IP
per
forms
the
actual
execution
of
a
function
independent
of
the
IP
controller.
Therefore
the
IP
controller
(an
Attached
Processor
with
associated
IP
control
software)
is
free
do
other
work
after
it
has
requested
execution
of
a
function
(except
that
it
must
refrain
from
requesting
a
second
function).
Altr~ugh
the
IP's
execution
of
any
given
function
necessarily
varies,
figure
4-6
shows
the
basic
sequence
of
steps
that
is
common
to
most
functions.
Note
that
the
IP
checks
for
faults
throughout
execution.
Function
execution
begi~~
when
the
IP
detects
that
the
opcode
field
of
the
function
request
area
mawed
by
window 4
has
been
written.
The
IP
sets
the
state
of
window 4
to
"in-progress"
dur
ing
the
function
execution
process
to
irrlicate
that
the
function
request
facility
is
"in
use".
The
IP
reads
the
opcode from
the
function
request
area
arrl
decodes
it.
After
decooing
the
opcode,
the
IP
fetches
the
operands
required
by
the
function
from
the
function
request
area.
It
then
performs
the
operation
am
updates
destination
operands
with
the
result(s).
If
the
function
produces
a
return-value,
the
IP
writes
it
into
the
corresponding
field
of
the
function
request
area.
The
IP
terminates
execution
by
updating
the
function
completion
state
subfield
arrl
generating
an
interrupt
(see
awendix
D
for
information
on
discriminating
IP
interrupts).
The
function
completion
state
subfield
irrlicates
successful
or
faulted
execution.
The
IP
records
additional
information
in
one
or
more
of
the
context,
process
arrl
processor
objects
when
it
detects
a
fault
during
execution
of
a
function.
4-4.
FUNcrICN
CDMPLErICN
Normally
the
IP
controller
will
use
the
IP's
interrupt
to
detect
function
completion;
it
may
also
poll
the
function
completion
state
subfield.
In
any
case,
the
function
completion
state
subfield
must
be
examined
to
determine
if
the
function
completed
successfully
or
faulted.
4-9