PD17012_15 Datasheet, PDF (208/320 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCONTROLLERS WITH DIGITAL TUNING SYSTEM HARDWARE

µPD17012, 17P012
17.4 Using IF Counter Function
The following subsections 17.4.1 through 17.4.3 explain how to use the hardware of the IF counter function,
program example, and count error.
17.4.1 Using hardware of IF counter
Figure 17-9 shows the block diagram illustrating how the P1B3/FMIFC and P1B2/AMIFC pins are used.
Table 17-1 shows the range of the frequencies that can be input to the P1B3/FMIFC and P1B2/AMIFC pins.
Because the input pins of the IF counter have an internal amplifier, cut off the DC component of the input
signal by using capacitor C as shown in Figure 17-9.
When the P1B3/FMIFC or P1B2/AMIFC pin is selected as the IF counter pin, switch SW turns ON, applying
a voltage of about 1/2VDD to each pin.
If the voltage has not risen to a sufficient intermediate level at this time, the AC amplifier does not operate
normally, and consequently, the IF counter does not correctly operate.
Therefore, make sure that a sufficiently long wait time elapses from the time each pin is selected as an IF
counter until counting is started.
Figure 17-9. Function of Each IF Counter Pin
R
SW
External frequency
C
FMIFC
AMIFC
Table 17-1. Input Frequency Range of IF Counter
Input Pin
P1B3/FMIFC
FMIF mode
P1B3/FMIFC
AMIF mode
P1B2/AMIFC
AMIF mode
Input Frequency
(MHz)
5 to 15
10.5 to 10.9
0.3 to 1
Input Amplitude
(Vp-p)
0.3
0.1
0.3
0.3 to 1
0.3
0.44 to 0.46
0.1
To internal counter
206
Data Sheet U10101EJ4V0DS