Datasheet

148
ATmega8A [DATASHEET]
8159E–AVR–02/2013
Receiver will have less noise resistance when the error ratings are high, especially for large serial frames (see
“Asynchronous Operational Range” on page 139). The error values are calculated using the following equation:
Error[%]
BaudRate
Closest Match
BaudRate
-------------------------------------------------------- 1–


100%=
Table 20-9. Examples of UBRR Settings for Commonly Used Oscillator Frequencies
Baud
Rate
(bps)
f
osc
= 1.0000MHz f
osc
= 1.8432MHz f
osc
= 2.0000MHz
U2X = 0 U2X = 1 U2X = 0 U2X = 1 U2X = 0 U2X = 1
UBRR Error UBRR Error UBRR Error UBRR Error UBRR Error UBRR Error
2400 25 0.2% 51 0.2% 47 0.0% 95 0.0% 51 0.2% 103 0.2%
4800 12 0.2% 25 0.2% 23 0.0% 47 0.0% 25 0.2% 51 0.2%
9600 6 -7.0% 12 0.2% 11 0.0% 23 0.0% 12 0.2% 25 0.2%
14.4k 3 8.5% 8 -3.5% 70.0%150.0%8 -3.5% 16 2.1%
19.2k 2 8.5% 6 -7.0% 50.0%110.0%6 -7.0% 12 0.2%
28.8k 1 8.5% 3 8.5% 3 0.0% 7 0.0% 38.5%8-3.5%
38.4k 1 -18.6% 2 8.5% 2 0.0% 5 0.0% 28.5%6-7.0%
57.6k 0 8.5% 1 8.5% 1 0.0% 3 0.0% 18.5%38.5%
76.8k – – 1 -18.6% 1 -25.0% 20.0%1 -18.6% 2 8.5%
115.2k – – 0 8.5% 0 0.0% 1 0.0% 08.5%18.5%
230.4k – – – – – – 00.0%–-––
250k––––––––––00.0%
Max
(1)
62.5 kbps 125 kbps 115.2 kbps 230.4 kbps 125 kbps 250 kbps
1. UBRR = 0, Error = 0.0%