ICM7216A Intersil Corporation, ICM7216A Datasheet - Page 9

• Manufacturer Part Number: ICM7216A
• Description: 8-digit, Multi-function, Frequency Counters/timers
• Manufacturer: Intersil Corporation

Frequency - In this mode input A is counted by the Main
Counter for a precise period of time. This time is determined
by the time base oscillator and the selected range. For the
10MHz (or 1MHz) time base, the resolutions are 100Hz,
10Hz, 1Hz and 0.1Hz. The decimal point on the display is
set for kHz reading.
Period - In this mode, the timebase oscillator is counted by
the Main Counter for the duration of 1, 10, 100 or 1000
(range selected) periods of the signal at input A. A 10MHz
timebase gives resolutions of 0.1 s to 0.0001 s for 1000
periods averaging. Note that the maximum input frequency
for period measurement is 2.5MHz.
Frequency Ratio - In this mode, the input A is counted by
the Main Counter for the duration of 1, 10, 100 or 1000
(range selected) periods of the signal at input B. The fre-
quency at input A should be higher than input B for meaning-
ful result. The result in this case is unitless and its resolution
can go up to 3 digits after decimal point.
Time Interval - In this mode, the timebase oscillator is
counted by the Main Counter for the duration of a 1-0 transi-
tion of input A until a 1-0 transition of input B. This means
input A starts the counting and input B stops it. If other ranges,
except 0.01s/1 cycle are selected the sequence of input A and
B transitions must happen 10, 100 or 1000 times until the
Frequency (f
Period (t
Ratio (f
Time Interval
(A B)
Unit Counter
(Count A)
Osc. Freq.
(f
OSC
FUNCTION
)
A
A
/f
)
B
)
A
TABLE 2. 7216A/B INPUT ROUTING
)
INTERNAL OR
OSCILLATOR
Input A
Oscillator
Input A
Oscillator
Input A
Oscillator
COUNTER
EXTERNAL
MAIN
INPUT A
INPUT B
INPUT A
100Hz
FIGURE 11. SIMPLIFIED BLOCK DIAGRAM OF FUNCTIONS IMPLEMENTATION
100Hz (Oscillator 10
Input A
Input B
Input A
Input B
Not Applicable
100Hz (Oscillator 10
REFERENCE COUNTER
ICM7216A, ICM7216B, ICM7216D
INTERNAL CONTROL
INTERNAL CONTROL
SELECTOR
SELECTOR
INPUT
INPUT
5
5
or 10
or 10
4
4
)
)
INTERNAL CONTROL
9-18
display becomes updated; note this when measuring long
time intervals to give enough time for measurement comple-
tion. The resolution in this mode is the same as for period
measurement. See the Time Interval Measurement section
also.
Unit Counter - In this mode, the Main Counter is always
enabled. The input A is counted by the Main Counter and
displayed continuously.
Oscillator Frequency - In this mode, the device makes a
frequency measurement on its timebase. This is a self test
mode for device functionality check. For 10MHz timebase
the display will show 10000.0, 10000.00, 10000.000 and
Overflow in different ranges.
Range Input
The RANGE INPUT selects whether the measurement
period is made for 1, 10, 100 or 1000 counts of the Refer-
ence Counter. As it is shown in Table 1, this gives different
counting windows for frequency measurement and various
cycles for other modes of measurement.
In all functional modes except Unit Counter, any change in
the RANGE INPUT will stop the present measurement
without updating the display and then initiate a new mea-
surement. This prevents an erroneous first reading after the
RANGE INPUT is changed.
Control Input
Unlike the other multiplexed inputs, to which only one of the
digit outputs can be connected at a time, this input can be
tied to different digit lines to select combination of controls.
In this case, isolation diodes must be used in digit lines to
avoid crosstalk between them (see Figure 17). The direction
of diodes depends on the device version, common anode or
common cathode. For maximum noise immunity at this input,
in addition to the 10K resistor which was mentioned before,
a 39pF to 100pF capacitor should also be placed between
this input and the V
Display Off - To disable the display drivers, it is necessary to
tie the D4 line to the CONTROL INPUT and have the HOLD
CLOCK
ENABLE
CLOCK
DD
REFERENCE COUNTER
INTERNAL CONTROL
RANGE SELECTOR
MAIN COUNTER
or V
1
SS
10
(See Figure 17).
100
1000