Datasheet

Section 15 Smart Card Interface

Rev.6.00 Sep. 27, 2007 Page 696 of 1268

REJ09B0220-0600

15.4 Usage Notes

The following points should be noted when using the SCI as a smart card interface.

Receive Data Sampling Timing and Receive Margin in Smart Card Interface Mode: In smart

card interface mode, the SCI operates on a base clock with a frequency of 32, 64, 372, or 256

times the transfer rate (determined by bits BCP1 and BCP0).

In reception, the SCI samples the falling edge of the start bit using the base clock, and performs

internal synchronization. Receive data is latched internally at the rising edge of the 16th, 32nd,

186th, or 128th pulse of the base clock. Use of a 372-times clock is illustrated in figure 15.10.

Internal

base

clock

372 clocks

186 clocks

Receive

data (RxD)

Synchro-

nization

sampling

timing

D0 D1

Data

sampling

timing

185

371 0

371

185

Start bit

Figure 15.10 Receive Data Sampling Timing in Smart Card Mode

(When Using 372-Times Clock)