ICM7226A, ICM7226B
Table 1 shows the functions selected by each digit for these The implementation of different functions is done by routing
inputs.
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.
TABLE 1. MULTIPLEXED INPUT FUNCTIONS
INPUT
FUNCTION
Frequency
DIGIT
D1
D8
D2
D5
D4
D3
D1
D2
D3
D4
D5
FUNCTION INPUT
Pin 4
Period
Frequency Ratio
Time Interval
Unit Counter
Oscillator Frequency
0.01s/1 Cycle
RANGE INPUT
Pin 21
0.1s/10 Cycles
1s/100 Cycles
10s/1K Cycles
Enable External Range Input
Display Off
CONTROL INPUT
Pin 1
D4 and
Hold
TABLE 2. INPUT ROUTING
MAIN
Display Test
D8
D2
D1
D3
FUNCTION
COUNTER
COUNTER
1MHz Select
5
4
Frequency (f )
A
Input A
100Hz (Oscillator ÷10 or 10 )
External Oscillator Enable
Period (t )
Oscillator
Input A
Input A
A
External Decimal Point
Enable
Ratio (f /f )
Input B
A
B
External DP INPUT
Pin 20
Decimal point is output for same digit
that is connected to this input.
Time Interval
(A→B)
Oscillator
Input A
Input B
Unit Counter
(Count A)
Input A
Not Applicable
Function Input
The six functions that can be selected are: Frequency,
Period, Time Interval, Unit Counter, Frequency Ratio and
Oscillator Frequency.
5
4
Osc. Freq.
Oscillator
100Hz (Oscillator ÷10 or 10 )
(f
)
OSC
INTERNAL CONTROL
INTERNAL CONTROL
100Hz
INPUT
SELECTOR
INPUT A
CLOCK
REFERENCE COUNTER
10 100
INPUT B
1
1000
÷
÷
÷
÷
INTERNAL CONTROL
RANGE SELECTOR
INTERNAL CONTROL
INTERNAL OR
EXTERNAL
OSCILLATOR
ENABLE
CLOCK
MAIN COUNTER
INPUT
SELECTOR
INPUT A
FIGURE 11. SIMPLIFIED BLOCK DIAGRAM OF FUNCTIONS IMPLEMENTATION
9-22
INTERSIL [ Intersil ]
