Digitally Filtered Inputs - NEC V850ES/F 3-L Series User Manual

Pin Functions

2.6.2 Digitally filtered inputs

Filter operation
Input terminal
Filter output
Figure 2-58
The input signal INTP3 is passed through both an analog and a digital filter.
The digital filter operates in all modes, in which fXX is available. Thus, it does
not operate in standby modes (if fXT is used as the sampling clock, it can
operate in standby modes). The digital filter is only effective if the
corresponding pin works in alternative input mode and not as a general
purpose I/O port.
The input terminal signal is sampled with the sampling frequency f
shorter than N-1 sampling cycles are suppressed and no internal signal is
generated. Pulses longer than N sampling cycles are recognized as valid
pulses and an internal signal is generated. The pulses between N-1 and N
sampling cycles are eliminated as noise, or detected as a valid edge. The
characteristics of the digital filter can be set by the NFC register.
The characteristic of the digital noise filter is determined by the register NFC:
• f is defined by NFC.NFC[2:0]
s
f is the sampling frequency. Together with N it defines the minimum input
s
terminal pulse width to be validated.
• N is defined by NFC.NFSTS
Possible values for N are 2 or 3.
The filter operation is illustrated in Figure 2-58 for NFC.NFSTS = 0 (N = 3).
Digital noise removal example for NFC.NFSTS = 0 (N = 3)
User's Manual U18743EE1V2UM00
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