Rev. 2.0, 11/00, page 560 of 1037
25.3.7
Noise Canceler
The logic levels at the SCL and SDA pins are routed through noise cancelers before being
latched internally. Figure 25.13 shows a block diagram of the noise canceler circuit.
The noise canceler consists of two cascaded latches and a match detector. The SCL (or SDA)
input signal is sampled on the system clock, but is not passed forward to the next circuit unless
the outputs of both latches agree. If they do not agree, the previous value is held.
SCL or SDA
input signal
Internal SCL
or SDA signal
Sampling clock
Sampling
clock
System clock
period
C
Latch
Q
D
C
Latch
Q
D
Match
detector
Figure 25.13 Block Diagram of Noise Canceler
25.3.8
Sample Flowcharts
Figures 25.14 to 25.17 show sample flowcharts for using the I
2
C bus interface in each mode.
Summary of Contents for Hitachi H8S/2191
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