ATmega88PA Automotive Atmel Corporation, ATmega88PA Automotive Datasheet - Page 194

• Manufacturer Part Number: ATmega88PA Automotive
• Manufacturer: Atmel Corporation

20.10 Examples of Baud Rate Setting
Table 20-4.
194
Baud
Rate
(bps)
2400
4800
9600
14.4k
19.2k
28.8k
38.4k
57.6k
76.8k
115.2k
230.4k
250k
Max.
Note:
(1)
1. UBRRn = 0, Error = 0.0%
Atmel ATmega48PA/88PA/168PA [Preliminary]
UBRRn
25
12
6
3
2
1
1
0
–
–
–
–
Examples of UBRRn Settings for Commonly Used Oscillator Frequencies
62.5 kbps
U2Xn = 0
Error
f
-18.6%
-7.0%
osc
0.2%
0.2%
8.5%
8.5%
8.5%
8.5%
–
–
–
–
= 1.0000MHz
5. When the last data frame is received by the addressed MCU, the addressed MCU sets
Using any of the 5- to 8-bit character frame formats is possible, but impractical since the
Receiver must change between using n and n+1 character frame formats. This makes
full-duplex operation difficult since the Transmitter and Receiver uses the same character size
setting. If 5- to 8-bit character frames are used, the Transmitter must be set to use two stop bit
(USBSn = 1) since the first stop bit is used for indicating the frame type.
Do not use Read-Modify-Write instructions (SBI and CBI) to set or clear the MPCMn bit. The
MPCMn bit shares the same I/O location as the TXCn Flag and this might accidentally be
cleared when using SBI or CBI instructions.
For standard crystal and resonator frequencies, the most commonly used baud rates for asyn-
chronous operation can be generated by using the UBRRn settings in
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
nous Operational Range” on page
equation:
Error[%]
UBRRn
the MPCMn bit and waits for a new address frame from master. The process then
repeats from 2.
51
25
12
8
6
3
2
1
1
0
–
–
U2Xn = 1
125 kbps
=
Error
-18.6%
BaudRate
------------------------------------------------------- - 1
-3.5%
-7.0%
0.2%
0.2%
0.2%
8.5%
8.5%
8.5%
8.5%
–
–
BaudRate
UBRRn
Closest Match
47
23
11
7
5
3
2
1
1
0
–
–
115.2 kbps
U2Xn = 0
Error
f
osc
-25.0%
–
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
–
–
= 1.8432MHz
191). The error values are calculated using the following
100%
UBRRn
95
47
23
15
11
230.4 kbps
U2Xn = 1
7
5
3
2
1
0
–
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
–
UBRRn
51
25
12
8
6
3
2
1
1
0
–
–
U2Xn = 0
125 kbps
Error
f
-18.6%
osc
-3.5%
-7.0%
0.2%
0.2%
0.2%
8.5%
8.5%
8.5%
8.5%
–
–
= 2.0000MHz
Table
UBRRn
103
51
25
16
12
20-4. UBRRn
9223B–AVR–09/11
8
6
3
2
1
–
0
U2Xn = 1
250 kbps
“Asynchro-
Error
-3.5%
-7.0%
0.2%
0.2%
0.2%
2.1%
0.2%
8.5%
8.5%
8.5%
0.0%
–