ICM7216B_04 Datasheet, PDF (10/18 Pages) Intersil Corporation – 8-Digit, Multi-Function, Frequency Counters/Timers

ICM7216B, ICM7216D
input (EX DP INPUT). Digit 8 should not be used since it will
override the overflow output. Leading zero blanking is
effective for the digits to the left of selected decimal point.
Hold Input
Except in the unit counter mode, when the HOLD input is
at VDD, any measurement in progress (before STORE goes
low) is stopped, the main counter is reset and the chip is
held ready to initiate a new measurement as soon as HOLD
goes low. The latches which hold the main counter data are
not updated, so the last complete measurement is displayed.
In unit counter mode when HOLD input is at VDD, the
counter is not stopped or reset, but the display is frozen at
that instantaneous value. When HOLD goes low the count
continues from the new value in the new counter.
RESET Input
The RESET input resets the main counter, stops any
measurement in progress, and enables the main counter
latches, resulting in an all zero output. A capacitor to ground
will prevent any hang-ups on power-up.
MEASUREMENT IN PROGRESS
This output is provided in lCM7216D. It stays low during
measurements and goes high for intervals between
measurements. It is provided for system interfacing and can
drive a low power Schottky TTL or one ECL load if the ECL
device is powered from the same supply as lCM7216D.
Decimal Point Position
Table 3 shows the decimal point position for different modes
of lCM7216 operation. Note that the digit 1 is the least
significant digit. Table 3 is for 10MHz timebase frequency.
Overflow Indication
When overflow happens in any measurement it will be
indicated on the decimal point of the digit 8. A separate LED
indicator can be used. Figure 9 shows how to connect this
indicator.
a
fb
g
ec
d
DP
FIGURE 9. SEGMENT IDENTIFICATION AND DISPLAY FONT
Overflow will be indicated on the decimal point output of
digit 8. A separate LED overflow indicator can be connected
as follows:
DEVICE
ICM7216B/D
CATHODE
D8
ANODE
Decimal Point
RANGE
0.01s/1 Cycle
0.1s/10 Cycle
1s/100 Cycle
10s/1K Cycle
FREQUENCY
D2
D3
D4
D5
TABLE 3. DECIMAL POINT POSITIONS
PERIOD
D2
D3
D4
D5
FREQUENCY
RATIO
D1
D2
D3
D4
TIME
INTERVAL
D2
D3
D4
D5
Time Interval Measurement
When in the time interval mode and measuring a single
event, the lCM7216B must first be “primed” prior to measuring
the event of interest. This is done by first generating a
negative going edge on Channel A followed by a negative
going edge on Channel B to start the “measurement interval”.
The inputs are then primed ready for the measurement.
Positive going edges on A and B, before or after the priming,
will be needed to restore the original condition.
Priming can be easily accomplished using the circuit in
Figure 10 (next page).
UNIT
COUNTER
D1
D1
D1
D1
OSCILLATOR
FREQUENCY
D2
D3
D4
D5
10