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SH7050 Datasheet, PDF (448/841 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperH RISC engine Family/ | |||
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Section 13 Serial Communication Interface (SCI)
16 clocks
8 clocks
Internal 0
base clock
78
15 0
78
â7.5 clocks +7.5 clocks
Receive
data (RxD)
Start bit
D0
15 0
5
D1
Synchronization
sampling timing
Data
sampling timing
Figure 13.23 Receive Data Sampling Timing in Asynchronous Mode
The receive margin in the asynchronous mode can therefore be expressed as:
( ) M = 0.5 â 1 â (L â 0.5) F â D â 0.5 (1 + F) Ã 100%
2N
N
M : Receive margin (%)
N : Ratio of clock frequency to bit rate (N = 16)
D : Clock duty cycle (D = 0â1.0)
L : Frame length (L = 9â12)
F : Absolute deviation of clock frequency
From the equation above, if F = 0 and D = 0.5 the receive margin is 46.875%:
D = 0.5, F = 0
M = (0.5 â 1/(2 Ã 16)) Ã 100%
= 46.875%
This is a theoretical value. A reasonable margin to allow in system designs is 20â30%.
Rev. 5.00 Jan 06, 2006 page 428 of 818
REJ09B0273-0500
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