ICM7226 Intersil Corporation, ICM7226 Datasheet - Page 18

• Manufacturer Part Number: ICM7226
• Description: 8-Digit Multi-Function Frequency Counter/Timer
• Manufacturer: Intersil Corporation

Figure 23 shows the use of a CD4016 analog multiplexer to
multiplex the digital outputs back to the FUNCTION Input.
Since the CD4016 is a digitally controlled analog transmission
gate, no level shifting of the digit output is required. CD4051s
or CD4052s could also be used to select the proper inputs for
the multiplexed input on the ICM7226 from 2-bit or 3-bit digital
inputs. These analog multiplexers may also be used in sys-
tems in which the mode of operation is controlled by a micro-
processor rather than directly from front panel switches. TTL
multiplexers such as the 74LS153 or 74LS251 may also be
used, but some additional circuitry will be required to convert
the digit output to TTL compatible logic levels.
The circuit shown in Figure 24 can be used in any of the
circuit applications shown to implement a single measure-
ment mode of operation. This circuit uses the STORE output
OUTPUT
FIGURE 24. SINGLE MEASUREMENT CIRCUIT FOR USE WITH
STORE
+5V
1
35
SWITCH
S1
S1
S2
S3
ICM7226
V
DD
S2
100k
Open-Single Meas Mode Enabled
Closed-Initiate New Measurement
Closed-Hold Input
D8
e
f
31 32 33 34
22 23 24 26
d
ICM7211
g
•
a
100k
V
FIGURE 26. 10MHz UNIVERSAL COUNTER SYSTEM WITH LCD DISPLAY
c
DD
b
•
FUNCTION
D5
28 SEGMENT LINES
e
f
d
g
a
S3
c
b
30 29 28 27
V
DD
100k
e
ICM7226A, ICM7226B
f
d
g
a
c
b
HOLD
INPUT
5
ICM7226A
7
e
f
9-32
d
6
g
a
c
17
to put the ICM7226 into a hold mode. The HOLD input can
also be used to reduce the time between measurements.
The circuit shown in Figure 25 puts a short pulse into the
HOLD input a short time after STORE goes low. A new mea-
surement will be initiated at the end of the pulse on the
HOLD input. This circuit reduces the time between measure-
ments to about 40ms from 200ms; use of the circuit shown in
Figure 25 on the circuit shown in Figure 21 will reduce the
time between measurements from 800ms to about 160ms.
Using LCD Display
Figure 26 shows the ICM7226 being interfaced to LCD dis-
plays, by using its BCD outputs and 8 digit lines to drive two
ICM7211 display drivers.
OUTPUT
FIGURE 25. CIRCUIT FOR REDUCING TIME BETWEEN
b
5
STORE
18
e
27
f
28 SEGMENT LINES
d
g
100k
100pF
a
28
c
MEASUREMENTS
b
29
30
e
f
d
g
a
D8
c
b
31 32 33 34
27 28 29 30
HOLD SWITCH
ICM7211
•
e
f
•
d
100pF
g
a
D1
c
b
V
DD
100k
N.O.
e
f
d
g
a
c
b
36
+5V
1
35
HOLD
INPUT