Section 16 Serial Communication Interface (SCI, IrDA, and CRC)
Rev. 3.00 Jan 25, 2006 page 419 of 872
REJ09B0286-0300
16.4.2
Receive Data Sampling Timing and Reception Margin in Asynchronous Mode
In asynchronous mode, the SCI operates on a basic clock with a frequency of 16 times the bit rate.
In reception, the SCI samples the falling edge of the start bit using the basic clock, and performs
internal synchronization. Since receive data is latched internally at the rising edge of the 8th pulse
of the basic clock, data is latched at the middle of each bit, as shown in figure 16.4. Thus the
reception margin in asynchronous mode is determined by formula (1) below.
M = (0.5 –
) –
– (L – 0.5) F
×
100 [%] ..... Formula (1)
1
2N
D – 0.5
N
{
}
M: Reception margin (%)
N: Ratio of bit rate to clock (N = 16)
D: Clock duty (D = 0.5 to 1.0)
L: Frame length (L = 9 to 12)
F: Absolute value of clock rate deviation
Assuming values of F = 0 and D = 0.5 in formula (1), the reception margin is determined by the
formula below.
M = {0.5 – 1/(2 × 16) } × 100[%] = 46.875%
However, this is only the computed value, and a margin of 20% to 30% should be allowed in
system design.
Internal
basic clock
16 clocks
8 clocks
Receive data
(RxD)
Synchronization
sampling timing
Start bit
D0
D1
Data sampling
timing
15 0
7
15 0
0
7
Figure 16.4 Receive Data Sampling Timing in Asynchronous Mode
Содержание H8S/2158
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Страница 47: ...Rev 3 00 Jan 25 2006 page xlv of lii Appendix Figure C 1 Package Dimensions TBP 112A 864...
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Страница 118: ...Section 3 MCU Operating Modes Rev 3 00 Jan 25 2006 page 64 of 872 REJ09B0286 0300...
Страница 126: ...Section 4 Exception Handling Rev 3 00 Jan 25 2006 page 72 of 872 REJ09B0286 0300...
Страница 198: ...Section 6 Bus Controller Rev 3 00 Jan 25 2006 page 144 of 872 REJ09B0286 0300...
Страница 326: ...Section 10 8 Bit PWM Timer PWM Rev 3 00 Jan 25 2006 page 272 of 872 REJ09B0286 0300...
Страница 440: ...Section 15 Watchdog Timer WDT Rev 3 00 Jan 25 2006 page 386 of 872 REJ09B0286 0300...
Страница 606: ...Section 17 I 2 C Bus Interface IIC Rev 3 00 Jan 25 2006 page 552 of 872 REJ09B0286 0300...
Страница 742: ...Section 19 Multimedia Card Interface MCIF Rev 3 00 Jan 25 2006 page 688 of 872 REJ09B0286 0300...
Страница 744: ...Section 20 Encryption Operation Circuit DES and GF Rev 3 00 Jan 25 2006 page 690 of 872 REJ09B0286 0300...
Страница 750: ...Section 21 D A Converter Rev 3 00 Jan 25 2006 page 696 of 872 REJ09B0286 0300...
Страница 768: ...Section 22 A D Converter Rev 3 00 Jan 25 2006 page 714 of 872 REJ09B0286 0300...
Страница 770: ...Section 23 RAM Rev 3 00 Jan 25 2006 page 716 of 872 REJ09B0286 0300...
Страница 824: ...Section 26 Clock Pulse Generator Rev 3 00 Jan 25 2006 page 770 of 872 REJ09B0286 0300...
Страница 844: ...Section 27 Power Down Modes Rev 3 00 Jan 25 2006 page 790 of 872 REJ09B0286 0300...
Страница 878: ...Section 28 List of Registers Rev 3 00 Jan 25 2006 page 824 of 872 REJ09B0286 0300...
Страница 926: ...Index Rev 3 00 Jan 25 2006 page 872 of 872 REJ09B0286 0300...