hd64338023s Renesas Electronics Corporation., hd64338023s Datasheet - Page 428

• Manufacturer Part Number: hd64338023s
• Description: Renesas 8-bit Single-chip Microcomputer Super Low Power Series
• Manufacturer: Renesas Electronics Corporation.

Section 10 Serial Communication Interface
Consequently, the receive margin in asynchronous mode can be expressed as shown in equation
(1).
Substituting 0 for F (absolute value of clock frequency deviation) and 0.5 for D (clock duty) in
equation (1), a receive margin of 46.875% is given by equation (2).
However, this is only a computed value, and a margin of 20% to 30% should be allowed when
carrying out system design.
Rev. 7.00 Mar 10, 2005 page 386 of 652
REJ09B0042-0700
Internal
basic clock
Receive data
(RXD32)
Synchronization
sampling timing
Data sampling
timing
M ={(0.5 –
where
When D = 0.5 and F = 0,
M = {0.5 – 1/(2 × 16)} • 100 [%]
= 46.875%
Figure 10.21 Receive Data Sampling Timing in Asynchronous Mode
M: Receive 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 frequency deviation
2N
1
0
8 clock pulses
Start bit
) –
D – 0.5
N
16 clock pulses
7
– (L – 0.5) F} • 100 [%]
15 0
D0
.... Equation (2)
..... Equation (1)
7
15 0
D1