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IBM 1 Series - Pulse Counter; Pulse Duration Counter; Timer Feature Operational Characteristics; Interrupts

IBM 1 Series
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Pulse
Counter
Pulse
Duration
Counter
Perform
the
following
steps
to
use
the
timer
as
a
pulse
counter
with
the
external
customer
clock
input:
1.
5.
The
Prepare
timer
0
to
interrupt
in
internal
mode
with
the
time
base
at
some
prescribed
interval
(for
example,
1
second).
Load
timer
1
with
a
value
that
is
larger
than
the
number
of
expected
external
pulses.
Set
up
timer
1
to
receive
customer
clock
(external
time
base)
in
aperiodic
mode.
Have
timer
O
interrupt
initiate
a
read
timer
1
value
in
the
processor.
Subtract
the
present
timer
1
value
from
the
original
value
of
timer
1.
Reload
the
starting
value
into
timer
1
to
repeat
the
cycle.
customer
clock
counts
per
second can be
read
into
the
processor.
Perform
the
following
steps
to
use
the
timer
as
a
pulse-duration
counter:
1.
2.
aA
YM
Ss
Prepare
timer.
Set
timer
period
and
initial
value
for a
value
greater
than
the
width
of
the
expected
pulse.
Set
timer
mode
for
external
gate
control
(bit
15
of
the
IDCB
data
word
set
to
1).
Start
timer.
‘Run
state’
to
customer
interface
becomes
active.
‘External
gate’
active
starts
the
timer,
and
it
starts
counting.
At
the
fall
of
‘external
gate,’
the
timer
stops
running
and
an
attention
interrupt
is
presented
to
the
channel.
Read
the
timer
and
subtract
present
value
from
original
value.
The
result
is
the
pulse
duration
of
the
‘external
gate’
line
in
terms
of the
time
base
selected.
Reload
the
starting
value
into
the
timer
to
repeat
the
cycle.
Timer
Feature
Operational
Characteristics
Interrupts
Reported
at
Interrupt
Time
3-8
GA34-0033
The
interrupt
condition
codes
(CCs)
are
described
in
this
section
to
aid
in
the
understanding
of
interrupt
presentation.
CC
Meaning
value
2
Exception
3
Device
end
4
Attention
6
Attention
and
exception
7
Attention
and
device
end
CC2
Exception—An
overrun
condition
has
occurred
in
the
timer.
Overrun
means
that
a
device-end
interrupt
condition
occurs
while
a
previous
device-end
interrupt
is
still
pending
in
the
timer.

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