Rainbow-electronics Atmega169L Manuel d'utilisateur télécharger pdf (Page 173)

173

ATmega169V/L

2514A–AVR–08/02

Examples of Baud Rate

Setting

For standard crystal and resonator frequencies, the most commonly used baud rates for

asynchronous operation can be generated by using the UBRR settings in Table 79.

UBRR values which yield an actual baud rate differing less than 0.5% from the target

baud rate, are bold in the table. Higher error ratings are acceptable, but the Receiver will

have less noise resistance when the error ratings are high, especially for large serial

frames (see “Asynchronous Operational Range” on page 165). The error values are cal-

culated using the following equation:

Error[%]

BaudRate

Closest Match

BaudRate

--------- ----------------- ------------ ------------------ 1–

100%•=

Table 79. Examples of UBRR Settings for Commonly Used Oscillator Frequencies

Baud

Rate

(bps)

osc

= 1.0000 MHz f

osc

= 1.8432 MHz f

osc

= 2.0000 MHz

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% 7 0.0% 15 0.0% 8 -3.5% 16 2.1%

19.2k 2 8.5% 6 -7.0% 5 0.0% 11 0.0% 6 -7.0% 12 0.2%

28.8k 1 8.5% 3 8.5% 3 0.0% 7 0.0% 3 8.5% 8 -3.5%

38.4k 1 -18.6% 2 8.5% 2 0.0% 5 0.0% 2 8.5% 6 -7.0%

57.6k 0 8.5% 1 8.5% 1 0.0% 3 0.0% 1 8.5% 3 8.5%

76.8k ––1 -18.6% 1 -25.0% 2 0.0% 1 -18.6% 2 8.5%

115.2k ––0 8.5% 0 0.0% 1 0.0% 0 8.5% 1 8.5%

230.4k ––––––00.0%––––

250k ––––––––––00.0%

Max.

(1)

62.5 kbps 125 kbps 115.2 kbps 230.4 Mbps 125 kpbs 250 kbps

1. UBRR = 0, Error = 0.0%

1 2 ... 168 169 170 171 172 173 174 175 176 177 178 ... 316 317

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