NEC PD78214 - Manual (Page 328)

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Chapter 11 Edge Detection Function
11
(5) If noise input to pins P21 to P26 is synchronized with the f
CLK
/4 clock of the µPD78214, it may not be judged
as being noise. If the input of such noise is possible, add a filter to the input pin so that the noise can be
eliminated.
(6) An in-circuit emulator cannot successfully eliminate digital noise. It may erroneously detect a falling edge due
to noise during the input of a low signal and a rising edge due to the noise during the input of a high signal
(see Fig. 11-6). When data is read from port 2, noise is not eliminated, being read instead.
Fig. 11-6 Erroneously Detected Edges
(a) Erroneously detected edge during input of low signal
INTPn input (n = 0 to 6)
Erroneously detected edge
f
CLK
/4
After noise rejection
Falling edge detection
Rising edge detection
Noise
"L"
(b) Erroneously detected edge during input of high signal
INTPn input (n = 0 to 6)
Erroneously detected edge
f CLK /4
After noise rejection
Falling edge detection
Rising edge detection
Noise
"L"
If the IE-78210-R is used, the real-time output port, timer/counter, and A/D converter operate according to the
erroneously detected edge. If another in-circuit emulator is used, these components operate as described below:
• Real-time output port : Operates according to the erroneously detected edge.
• A/D converter : Operates according to the erroneously detected edge.
• Capture or clear operation of the timer/counter : Carried out independently of the erroneously detected edge.
Even if the erroneously detected edge causes an interrupt,
the capture value is not updated. The value of CR22
becomes undefined after it has been read by the CPU.