ICM7226A_01 Datasheet, PDF (8/19 Pages) Intersil Corporation – 8-Digit, Multi-Function, Frequency Counter/Timer

ICM7226A, ICM7226B
Table 1 shows the functions selected by each digit for these
inputs.
TABLE 1. MULTIPLEXED INPUT FUNCTIONS
INPUT
FUNCTION
DIGIT
FUNCTION INPUT
Frequency
D1
Pin 4
Period
D8
Frequency Ratio
D2
Time Interval
D5
Unit Counter
D4
Oscillator Frequency
D3
RANGE INPUT
0.01s/1 Cycle
D1
Pin 21
0.1s/10 Cycles
D2
1s/100 Cycles
D3
10s/1K Cycles
D4
Enable External Range Input D5
CONTROL INPUT
Pin 1
Display Off
D4 and
Hold
Display Test
D8
1MHz Select
D2
External Oscillator Enable
D1
External Decimal Point
D3
Enable
External DP INPUT
Pin 20
Decimal point is output for same digit
that is connected to this input.
Function Input
The six functions that can be selected are: Frequency,
Period, Time Interval, Unit Counter, Frequency Ratio and
Oscillator Frequency.
The implementation of different functions is done by routing
the different signals to two counters, called “Main Counter”
and “Reference Counter”. A simplified block diagram of the
device for functions realization is shown in Figure 11. Table 2
shows which signals will be routed to each counter in differ-
ent cases. The output of the Main Counter is the information
which goes to the display. The Reference Counter divides its
input to 1, 10, 100 and 1000. One of these outputs will be
selected through the range selector and drive the enable
input of the Main Counter. This means that the Reference
Counter, along with its' associated blocks, directs the Main
Counter to begin counting and determines the length of the
counting period. Note that Figure 11 does not show the com-
plete functional diagram (See the Functional Block Dia-
gram). After the end of each counting period, the output of
the Main Counter will be latched and displayed, then the
counter will be reset and a new measurement cycle will
begin. Any change in the FUNCTION INPUT will stop the
present measurement without updating the display and then
initiate a new measurement. This prevents an erroneous first
reading after the FUNCTION INPUT is changed. In all
cases, the 1-0 transitions are counted or timed.
FUNCTION
Frequency (f_A)
Period (t_A)
Ratio (f_A/f_B)
Time Interval
(A→B)
Unit Counter
(Count A)
Osc. Freq.
(f_OSC)
TABLE 2. INPUT ROUTING
MAIN
COUNTER
Input A
Oscillator
Input A
Oscillator
Input A
COUNTER
100Hz (Oscillator ³÷10⁵ or 10⁴)
Input A
Input B
Input A
Input B
Not Applicable
Oscillator
100Hz (Oscillator ³÷10⁵ or 10⁴)
100Hz
INPUT A
INPUT B
INTERNAL OR
EXTERNAL
OSCILLATOR
INPUT A
INTERNAL CONTROL
INTERNAL CONTROL
INPUT
SELECTOR
INTERNAL CONTROL
INTERNAL CONTROL
CLOCK
REFERENCE COUNTER
÷1 ÷10 ÷100 ÷1000
RANGE SELECTOR
INPUT
SELECTOR
ENABLE
CLOCK
MAIN COUNTER
FIGURE 11. SIMPLIFIED BLOCK DIAGRAM OF FUNCTIONS IMPLEMENTATION
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