ICM7226 Intersil Corporation, ICM7226 Datasheet - Page 10

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

RST IN Input
The RST IN is provided to reset the Main Counter, stop any
measurement in progress, and enable the display latches,
resulting in the all zero display. It is suggested to have a
capacitor at this input to V
on power up. See application circuits.
EXT RANGE Input
This input is provided to select ranges other than those
provided in the chip. In any mode of measurement the duration
of measurement is determined by the EXT RANGE if this input
is enabled. This input is sampled at 10ms intervals by the
100Hz reference derived from the timebase. Figure 12 shows
the relationship between this input, 100Hz reference signal and
MEAS IN PROGRESS. EXT RANGE can change state
anywhere during the period of 100Hz reference by will be
sampled at the trailing edge of the period to start or stop
measurement.
This input should not be used for short arbitrary ranges
(because of its sampling period), it is provided for very long
gating purposes. A way of using the ICM7226 for a short
arbitrary range is to feed the gating signal into the INPUT B
and run the device in the Frequency Ratio mode. Note that
the gating period will be from one positive edge until the next
positive edge of INPUT B (0.01s/1 cycle range).
MEAS IN PROGRESS, STORE, RST OUT Outputs
These outputs are provided for external system interfacing.
MEAS IN PROGRESS stays low during measurements and
goes high for intervals between measurements. Figure 13
shows the relationship between these outputs for intervals
between measurements. All these outputs can drive a low
power Schottky TTL. The MEAS IN PROGRESS can drive
one ECL load if the ECL device is powered from the same
power supply as the ICM7226.
FIGURE 12. EXTERNAL RANGE INPUT TO END OF
0.01s/1 Cycle
0.1s/10 Cycle
1s/100 Cycle
10s/1K Cycle
External
IN PROGRESS
REFERENCE
EXT RANGE
COUNTER
CLOCK
INPUT
MEAS
RANGE
MEASUREMENT IN PROGRESS
t
r
SS
FREQUENCY
to prevent any hangup problem
N/A
D2
D3
D4
D5
TABLE 4. DECIMAL POINT POSITIONS
PERIOD
ICM7226A, ICM7226B
N/A
D2
D3
D4
D5
FREQUENCY
9-24
RATIO
BCD Outputs
The BCD representation of each display digit is available at
the BCD outputs in a multiplexed fashion. See Table 3 for dig-
its truth table. The BCD output of each digit is available when
its corresponding digit output is activated. Note that the digit
outputs are multiplexed from D8 (MSD) to D1 (LSD). The pos-
itive going (ICM7226A, common anode) or the negative going
(ICM7226B, common cathode) digit drive signals lag the BCD
data by 2 s to 6 s. This starting edge of each digit drive sig-
nal should be used to externally latch the BCD data. Each
BCD output drives one low power Schottky TTL load. Leading
zero blanking has no effect on the BCD outputs.
BUF OSC OUT Output
The BUFFered OSCillator OUTput is provided for use of the
on-board oscillator signal, without loading the oscillator itself.
This output can drive one low power Schottky TTL load. Care
should be taken to minimize capacitive loading on this pin.
Decimal Point Position
Table 4 shows the decimal point position for different modes
of lCM7226 operation. Note that the digit 1 is the least signif-
icant digit. Table is given for 10MHz timebase frequency.
FIGURE 13. RESET OUT, STORE AND MEASUREMENT IN
N/A
D1
D2
D3
D4
IN PROGRESS
NUMBER
RESET OUT
0
1
2
3
4
5
6
7
8
9
STORE
MEAS
TABLE 3. TRUTH TABLE BCD OUTPUTS
PROGRESS OUTPUTS BETWEEN MEASUREMENTS
INTERVAL
BCD 8
PIN 7
30ms TO
TIME
N/A
0
0
0
0
0
0
0
0
1
1
D2
D3
D4
D5
40ms
BCD 4
PIN 6
190ms TO 200ms
0
0
0
0
1
1
1
1
0
0
COUNTER
UNIT
N/A
D1
D1
D1
D1
40ms
BCD 2
PIN 17
60ms
0
0
1
1
0
0
1
1
0
0
OSCILLATOR
FREQUENCY
40ms
N/A
D2
D3
D4
D5
PIN 18
BCD 1
0
1
0
1
0
1
0
1
0
1