ATMEGA16U2-16AU Atmel, ATMEGA16U2-16AU Datasheet - Page 163

• Manufacturer Part Number: ATMEGA16U2-16AU
• Description: 8-bit Microcontrollers - MCU 16K Flash
• Manufacturer: Atmel

Specifications of ATMEGA16U2-16AU

• Product Category: 8-bit Microcontrollers - MCU
• Rohs: yes
• Core: AVR
• Data Bus Width: 8 bit
• Program Memory Size: 16 KB
• Data Ram Size: 1.25 KB
• Data Rom Size: 512 B
• Program Memory Type: Flash
• Factory Pack Quantity: 1250

18.8.3
7799D–AVR–11/10
Asynchronous Operational Range
R
slow
=
Figure 18-7. 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
bit.
The following equations can be used to calculate the ratio of the incoming data rate and internal
receiver baud rate.
------------------------------------------- -
S 1
D
S
S
S
R
Table 18-2
that Normal Speed mode has higher toleration of baud rate variations.
F
M
slow
–

D
+
18-2) base frequency, the Receiver will not be able to synchronize the frames to the start
(U2X = 0)
(U2X = 1)
Sample
Sample
+
D S 
RxD
1
S
and
+
S
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
mode.
First sample number used for majority voting. S
for Double Speed mode.
Middle sample number used for majority voting. S
S
is the ratio of the slowest incoming data rate that can be accepted in relation to the
receiver baud rate. R
accepted in relation to the receiver baud rate.
F
M
Table 18-3
= 5 for Double Speed mode.
Figure
1
1
2
18-7. For Double Speed mode the first low level must be delayed to
list the maximum receiver baud rate error that can be tolerated. Note
3
2
4
fast
5
3
is the ratio of the fastest incoming data rate that can be
6
7
4
8
STOP 1
ATmega8U2/16U2/32U2
9
5
R
10
fast
(A)
0/1
6
=
0/1
F
------------------------------------ -

D
= 8 for normal speed and S
M
(B)
0/1
0/1

+
= 9 for normal speed and
D
1
+
S
2
+
S
S
M
(C)
F
163
= 4