h8s-2649 Renesas Electronics Corporation., h8s-2649 Datasheet - Page 441

• Manufacturer Part Number: h8s-2649
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2600 Series
• Manufacturer: Renesas Electronics Corporation.

13.7.4
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 13.25, 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 –
Where M: Reception margin (%)
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%
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
Receive Data Sampling Timing and Reception Margin in Smart Card Interface
Mode
2N
1
) – (L – 0.5) F –
| D – 0.5 |
N
(1 + F) |
Section 13 Serial Communication Interface (SCI)
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Rev. 2.00 Dec. 05, 2005 Page 403 of 724
REJ09B0200-0200