Control Sequence; Control Sequence Diagram - Racal Instruments 9901 Maintenance Manual

CONTROL
SEQUENCE
3.
16
Figure
3.7 shows
the control
sequence diagrammatical
ly
(not to scale).
The
longer display time
shown
in
the
diagram applies
to
the latched
modes (Frequency,
Period
and
Ratio).
DISPLAY TIMES
HOLD TIME
J
I
'
H
I
I
MAIN GATE
(INTERNAL)
GATE OPEN
1
l'O'X'*,
1
1
It
,
i'
1
1
^
^
1
—
11
SO
5»is
DATA UPDATE
(INTERNAL)
RESET
(INTERNAL)
'
I
I
1
^100
ps
***
Control
Sequence Diagram
Fig.
3.7
External
Hold
3.17
If,
when
used with external circuitry,
it is
required to
extend
the
cycle
time,
the external hold
signal (logic
'0') at
pin 6 of
the data connector,
must be
applied before the
end of the gate or hold time.
To allow a
new
measurement
cycle
to
commence,
the external
hold input
must go
'high' for
not
less
than 200
ps.
External Reset
3.18
External reset
is
achieved by the application of logic
'O'
to
pin
7 of the connector
for
a period of not
less
than 5 ms;
on
reverting
to
'1'
level this
will reset
the dis-
play
to
'all
zeros'
and
initiate
a
new measurement
cycle.
3-8
9901 Vol. 2