3069RF-ZTAT Datasheet, PDF (559/1003 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER

14.4 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 372 times the transfer
rate. In reception, the SCI synchronizes internally with the fall of the start bit, which it samples on
the base clock. Receive data is latched at the rising edge of the 186th base clock pulse. The timing
is shown in figure 14.11.
372 clocks
186 clocks
0
185
371 0
Internal base
clock
185
371 0
Receive data
(RxD)
Start bit
D0
D1
Synchronization
sampling timing
Data sampling
timing
Figure 14.11 Receive Data Sampling Timing in Smart Card Interface Mode
Rev. 5.0, 09/04, page 537 of 978