UPD17717 Datasheet, PDF (334/408 Pages) NEC – 4-BIT SINGLE-CHIP MICROCONTROLLERS WITH DEDICATED HARDWARE FOR DIGITAL TUNING SYSTEM

µPD17717, 17718, 17719
18.4 Using IF Counter
The following sections 18.4.1 through 18.4.3 describe how to use the hardware of the IF counter, a program
example, and count error.
18.4.1 Using hardware of IF counter
Figure 18-9 shows the block diagram when the P1C0/FMIFC and P1C1/AMIFC pins.
As shown in the figure, the IF counter uses an input pin with an AC amplifier, the DC component of the input signal
must be cut with a capacitor.
When the P1C0/FMIFC or P1C1/AMIFC pin is selected for the IF counter function, switch SW turns ON, and the
voltage level on each pin reaches about 1/2VDD.
If the voltage has not risen to a sufficient intermediate level at this time, the IF counter does not operate normally
because the AC amplifier is not in the normal operating range.
Therefore, make sure that a sufficient wait time elapses after each pin has been specified to be used for the IF
counter until counting is started.
Figure 18-9. IF Count Function Block Diagram of Each Pin
External frequecny
C
FMIFC
AMIFC
R
SW
To internal counter
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