Fujitsu FR81S User Manual
CHAPTER 40: MULTI-FUNCTION SERIAL INTERFACE
5. Operation of UART
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER : MULTI-FUNCTION SERIAL INTERFACE
FUJITSU SEMICONDUCTOR CONFIDENTIAL
169
10/11 ∗ FLmax = (11bit ∗ (V+1)
−
(V+1) / 2) / φ = (21/20 ∗ 11 ∗ (V+1) / 2) / φ (s)
V: Reload value φ: Bus clock
When margin (φ) of the sampling timing is made two clocks, the allowance and maximum transfer rate
(FLmax) is as follows:
FLmax = (21/20 ∗ 11 ∗ (V+1)
−
2) / φ = (231V+191) / 20φ (s)
V: Reload value φ: Bus clock
Therefore, the allowed minimum baud rate (BGmin) at the destination would be calculated as follows.
BGmin = 11 / FLmax = 220φ / (231V+191) (bps)
V: Reload value φ: Bus clock
The allowed baud rate errors at UART and the destination can be obtained from above minimum/maximum
baud rate calculation formulas, the result of which are as follows.
Table 5-2 Allowed Baud Rate Error
Reload value Allowed maximum baud
rate error
Allowed minimum baud rate error
3
0%
0%
10
2.98%
-3.24%
50
4.37%
-4.44%
100
4.56%
-4.60%
200
4.66%
-4.68%
32767
4.76%
-4.76%
Note:
The accuracy of reception depends on the number of bits in a frame, bus clock, and the reload value. The
higher the bus clock and the division ratio are, the more accurate it will become.
MB91520 Series
MN705-00010-1v0-E
1482