r4f2426 Renesas Electronics Corporation., r4f2426 Datasheet - Page 926

• Manufacturer Part Number: r4f2426
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

Section 15 Serial Communication Interface (SCI, IrDA)
15.7.4
Only the internal clock generated by the on-chip baud rate generator is used as transmit/receive
clock in Smart Card interface. In Smart Card interface mode, the SCI operates on a basic clock
with a frequency of 32, 64, 372, 256, 93, 128, 186, or 512 times the bit rate (fixed at 16 times in
normal asynchronous mode) as determined by bits BCP2 to 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 15.25, by sampling receive data at the rising-edge of the 16th, 32nd, 186th, 128th,
46th, 64th, 93rd, or 256th pulse of the basic clock, data can be latched at the middle of the bit. The
reception margin is given by the following formula.
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.
Rev. 1.00 Sep. 19, 2008 Page 898 of 1270
REJ09B0466-0100
M =  (0.5 –
N: Ratio of bit rate to clock (N = 32, 64, 372, 256, 93, 128, 186, or 512)
D: Clock duty cycle (D = 0 to 1.0)
L: Frame length (L = 10)
F: Absolute value of clock frequency deviation
M = (0.5 – 1/2 × 372) × 100%
Receive Data Sampling Timing and Reception Margin
= 49.866%
2N
1
) – (L – 0.5) F –
D – 0.5
N
(1 + F)  × 100 [%]