hd66100 Renesas Electronics Corporation., hd66100 Datasheet - Page 236

• Manufacturer Part Number: hd66100
• Description: H8/3867 Series
• Manufacturer: Renesas Electronics Corporation.

9.5.3
The noise canceler consists of a digital low-pass filter that eliminates high-frequency component
noise from the pulses input from the input capture input pin. The noise canceler is set by NCS* in
PMR3.
Figure 9.8 shows a block diagram of the noise canceler.
The noise canceler consists of five latch circuits connected in series and a match detector circuit.
When the noise cancellation function is not used (NCS = 0), the system clock is selected as the
sampling clock When the noise cancellation function is used (NCS = 1), the sampling clock is the
internal clock selected by CKS1 and CKS0 in TMG, the input capture input is sampled on the
rising edge of this clock, and the data is judged to be correct when all the latch outputs match. If
all the outputs do not match, the previous value is retained. After a reset, the noise canceler output
is initialized when the falling edge of the input capture input signal has been sampled five times.
Therefore, after making a setting for use of the noise cancellation function, a pulse with at least
five times the width of the sampling clock is a dependable input capture signal. Even if noise
cancellation is not used, an input capture input signal pulse width of at least 2ø or 2ø
necessary to ensure that input capture operations are performed properly
Note: * An input capture signal may be generated when the NCS bit is modified.
Input capture
input signal
Sampling clock
Noise Canceler
Sampling
D
clock
Latch
C
Q
t: Set by CKS1 and CKS0
t
D
Figure 9.8 Noise Canceler Block Diagram
Latch
C
Q
D
Latch
C
Q
D
Latch
C
Q
D
Latch
C
Q
detector
Match
SUB
is
Noise
canceler
output
221