Special
Function
#4
Load
Interval Timer
(LIT)
General Description
I Code
Privileged
Instructions
• This Special Function loads
the
Interval
Timer
with
a halfword. 'The
address
of
the
halfword to be loaded is indicated by
the
contents
of
the
memory location addressed by
the
address field of the
Function
Call instruc-
tion.
If
the
value loaded is a nonzero value,
the
timer
begins to decrement
by one.
If
the
value loaded is zero, and
the
timer
is not counting,
the
instruction has no effect.
If
this
instruction is executed while the
timer
is
running,
the
contents of the counter
are
replaced by
the
specified halfword.
If
the specified halfword is zero,
the
timer
is
reset
to zero (shut-off)
and
no
interrupt
occurs
for
this
condition.
• 02.
Format Base
Displacement
Condition Code
Interrupt Action
Notes
034
• Unchanged.
•
Address
Error.
Power
Failure.
Machine Check.
Paging
Error.
Paging
Queue.
15
• 1.
If
either
this
Special
Function
or
the
timer
halfword addresses
are
not
on halfword boundaries,
an
Addressing
Error
Interrupt
condi-
tion occurs.
2.
If
the
counter
is
reset
to zero
after
zero occurs
and
the
interrupt
flag
has
been set,
the
interrupt
flag will
not
be cleared.
3.
Use
of
the
Interval
Timer
and
Diagnostic
Snapshot
by
programs
may
not
occur together, since
the
counter
register
is
common to both.
If
the
Diagnose function is
initiated
while
the
Interval
Timer
is
running,
the
shared
counter is cleared to zero
without
occurrence
of
the
Interval
Timer
Interrupt
and
the
Diagnose function assumes
control
of
the
counter.
If
the function being diagnosed is
the
Load
Interval
Timer,
the
actual loading
of
the
counter is inhibited
but
the
E.
O.
Flow is Diagnosed.
97
To Next Page
Loading...
Need help?
General
