Erroneously Detected Edges - NEC PD78212 User Manual

(5) If noise input to pins P21 to P26 is synchronized with the f
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.
INTPn input (n = 0 to 6)
After noise rejection
Falling edge detection
Rising edge detection
INTPn input (n = 0 to 6)
After noise rejection
Falling edge detection
Rising edge detection
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
• Capture or clear operation of the timer/counter : Carried out independently of the erroneously detected edge.
Fig. 11-6 Erroneously Detected Edges
(a) Erroneously detected edge during input of low signal
f /4
CLK
(b) Erroneously detected edge during input of high signal
f /4
CLK
: Operates according to the erroneously detected edge.
Chapter 11 Edge Detection Function
/4 clock of the µ PD78214, it may not be judged
CLK
Noise
"L"
Erroneously detected edge
Noise
"L"
Erroneously detected edge
Even if the erroneously detected edge causes an interrupt,
the capture value is not updated.
becomes undefined after it has been read by the CPU.
11
The value of CR22
299