Rev. 1.0, 09/02, page 343 of 568
14.7.4
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 32, 64, 372,
or 256 times the transfer rate (fixed at 16 times in normal asynchronous mode) as determined by
bits BCP1 and BCP0. In reception, the SCI samples the falling edge of the start bit using the basic
clock, and performs internal synchronization. As shown in figure 14.25, by sampling receive data
at the rising-edge of the 16th, 32nd, 186th, or 128th pulse of the basic clock, data can be latched at
the middle of the bit. The reception margin is given by the following formula.
M = | (0.5 –
) – (L – 0.5) F –
(1 + F) | 100%
1
2N
| D – 0.5 |
N
Where M: Reception margin (%)
N: Ratio of bit rate to clock (N = 32, 64, 372, and 256)
D: Clock duty cycle (D = 0 to 1.0)
L: Frame length (L = 10)
F: Absolute value of clock frequency deviation
Assuming values of F = 0, D = 0.5 and N = 372 in the above formula, the reception margin
formula is as follows.
M = (0.5 – 1/2
×
372)
×
100%
=
49.866%
Internal
basic clock
372 clocks
186 clocks
Receive data
(RxD)
Synchronization
sampling timing
D0
D1
Data sampling
timing
185
371 0
371
185
0
0
Start bit
Figure 14.25 Receive Data Sampling Timing in Smart Card Mode
(Using Clock of 372 Times the Transfer Rate)
Summary of Contents for H8S/2627
Page 22: ...Rev 1 0 09 02 page xx of xxxvi Index 565 ...
Page 30: ...Rev 1 0 09 02 page xxviii of xxxiv ...
Page 36: ...Rev 1 0 09 02 page xxxiv of xxxiv Table 23 9 Flash Memory Characteristics 561 ...
Page 82: ...Rev 1 0 09 02 page 46 of 568 ...
Page 88: ...Rev 1 0 09 02 page 52 of 568 ...
Page 98: ...Rev 1 0 09 02 page 62 of 568 ...
Page 156: ...Rev 1 0 09 02 page 120 of 568 ...
Page 390: ...Rev 1 0 09 02 page 354 of 568 ...
Page 480: ...Rev 1 0 09 02 page 444 of 568 ...
Page 512: ...Rev 1 0 09 02 page 476 of 568 ...
Page 528: ...Rev 1 0 09 02 page 492 of 568 ...
Page 580: ...Rev 1 0 09 02 page 544 of 568 ...