OPERATIONAL
PROCEDURES
Transmission Procedure
Response Procedure
Multi-Processor Installation
• The following sections
are
furnished
to
illustrate
typical operational
procedures when using
the
Direct Control feature. They
are
presented
for
clarification only and
are
not
meant
to imply fixed
and
firm
standards.
For
a detailed description
of
the
actual
programming
procedures, reference
should be made to
the
applicable reference
manuals
.
• User Program - (PI) The
user
program
in Processing
State
(PI)
contains a Supervisor Call instruction
with
a
Write
Direct
Interrupt
Code.
In
addition,
it
contains
the
following
parameters
required when
interrupt
is effected to the
operating
system in processor
state
(P3):
Data
Byte (8-bit code)
Signal Byte (specifies processor
(s)
to which
Write
Direct is addressed)
Return
Address
(for
return
to normal processing)
Operating
System
-
(P
3)
The
operating
system accepts
the
Super-
visor Call
Interrupt
and issues a
Program
Control
instruction
to
(P
2
).
In
addition,
the
locations
of
the
user
parameters
are
saved,
the
processor is
set
to the Privileged Mode and a change made
from
(P
3
)
to
(P
2
).
Supervisor Call Routine -
(PrJ)
The
Interrupt
Weight is used to
branch
to
the
Supervisor Call routine where
the
Supervisor
Call
Interrupt
Code is decoded
and
a
branch
is made to
the
required routine, in
this
case
the
Write
Direct routine. The
Write
Direct routine
then
performs
the
following:
1. Checks to determine
whether
Write
Direct
instruction
can be issued
or
must
be stacked in queue.
2. Fetches
the
user
parameters.
3. Sets
Write
Direct instruction I-Field to
the
Signal byte,
the
Address
field to
the
Data
byte,
and
the
Return
After
Interrupt
to
the
user
Return
Address
in
(PI).
4. Executes
Write
Direct instruction.
5.
If
no acknowledgement is received, sets control in Acknowledge queue.
6.
Set
processor to non-privileged mode.
7.
After
interrupt,
executes
Program
Control
instruction
and
branch
to
user
return
address in
(PI)
.
• Operating
System
-
(P
3
)
The
operating
system accepts
the
Direct
Control
Interrupt
and issues a
Program
Control
instruction
to
(P
2
).
In
addition, the processor is
set
to privileged mode
and
a change made
from
(P
3
)
to
(P
2
).
Read Direct Routine -
(PrJ)
The
Interrupt
Weight is used to
branch
to
the
Read Direct routine. The Read Direct routine
then
performs
the
following:
1. Issues a Read Direct instruction to
read
the
Data
Byte.
2.
Saves the
Data
Byte and
the
External
Interrupt
number
(which
corresponds to the
transmitting
processor)
for
user
Read Direct
processing.
86
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