ATmega1281R231 Atmel Corporation, ATmega1281R231 Datasheet - Page 220

• Manufacturer Part Number: ATmega1281R231
• Manufacturer: Atmel Corporation

Specifications of ATmega1281R231

• Flash (kbytes): 128 Kbytes
• Max. Operating Frequency: 16 MHz
• Max I/o Pins: 54
• Spi: 3
• Twi (i2c): 1
• Uart: 2
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Crypto Engine: AES
• Sram (kbytes): 8
• Eeprom (bytes): 4096
• Operating Voltage (vcc): 1.8 to 3.6
• Timers: 6
• Frequency Band: 2.4 GHz
• Max Data Rate (mb/s): 2
• Antenna Diversity: Yes
• External Pa Control: Yes
• Power Output (dbm): 3
• Receiver Sensitivity (dbm): -101
• Receive Current Consumption (ma): 13.2
• Transmit Current Consumption (ma): 14.4
• Link Budget (dbm): 104

22.7.3
2549N–AVR–05/11
Asynchronous Operational Range
Figure 22-7. Stop Bit Sampling and Next Start Bit Sampling
The same majority voting is done to the stop bit as done for the other bits in the frame. If the stop
bit is registered to have a logic 0 value, the Frame Error (FEn) Flag will be set.
A new high to low transition indicating the start bit of a new frame can come right after the last of
the bits used for majority voting. For Normal Speed mode, the first low level sample can be at
point marked (A) in
(B). (C) marks a stop bit of full length. The early start bit detection influences the operational
range of the Receiver.
The operational range of the Receiver is dependent on the mismatch between the received bit
rate and the internally generated baud rate. If the Transmitter is sending frames at too fast or too
slow bit rates, or the internally generated baud rate of the Receiver does not have a similar (see
Table 22-2 on page
frames to the start bit.
The following equations can be used to calculate the ratio of the incoming data rate and internal
receiver baud rate.
D
S
S
S
R
F
M
slow
(U2X = 0)
(U2X = 1)
Sample
Sample
RxD
R
slow
mode.
for Double Speed mode.
S
receiver baud rate. R
accepted in relation to the receiver baud rate.
Sum of character size and parity size (D = 5 to 10 bit).
Samples per bit. S = 16 for Normal Speed mode and S = 8 for Double Speed
First sample number used for majority voting. S
Middle sample number used for majority voting. S
is the ratio of the slowest incoming data rate that can be accepted in relation to the
=
M
= 5 for Double Speed mode.
------------------------------------------ -
S 1
–
Figure
221) base frequency, the Receiver will not be able to synchronize the
(
D
+
1
1
+
D S ⋅
1
2
22-7. For Double Speed mode the first low level must be delayed to
)S
+
3
2
S
ATmega640/1280/1281/2560/2561
F
4
fast
5
3
is the ratio of the fastest incoming data rate that can be
6
7
4
8
STOP 1
9
5
10
R
fast
(A)
0/1
6
=
0/1
F
-----------------------------------
(
= 8 for normal speed and S
D
(B)
0/1
0/1
(
+
D
M
1
+
= 9 for normal speed and
)S
2
)S
+
S
M
(C)
F
220
= 4