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12.4
Usage Note
The following points should be noted when using the SCI as a smart card interface.
Receive Data Sampling Timing and Reception Margin in Smart Card Interface Mode: In
smart card interface mode, the SCI operates on a basic clock with a frequency of 372 times the
transfer rate.
In reception, the SCI samples the falling edge of the start bit using the basic clock, and performs
internal synchronization. Receive data is latched internally at the rising edge of the 186th pulse of
the basic clock. This is illustrated in figure 12-7.
186 clocks
0
Internal
basic
clock
Receive
data (RxD)
Synchro-
nization
sampling
timing
Data
sampling
timing
Figure 12-7 Receive Data Sampling Timing in Smart Card Mode
408
372 clocks
185
371
0
Start bit
185
D0
371 0
D1
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