ATMEGA328P-20PU Atmel, ATMEGA328P-20PU Datasheet - Page 189

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ATMEGA328P-20PU

Manufacturer Part Number
ATMEGA328P-20PU
Description
Manufacturer
Atmel
Datasheet

Specifications of ATMEGA328P-20PU

Cpu Family
ATmega
Device Core
AVR
Device Core Size
8b
Frequency (max)
20MHz
Interface Type
SPI/TWI/USART
Program Memory Type
Flash
Program Memory Size
32KB
Total Internal Ram Size
2KB
# I/os (max)
23
Number Of Timers - General Purpose
3
Operating Supply Voltage (typ)
3.3/5V
Operating Supply Voltage (max)
5.5V
Operating Supply Voltage (min)
2.7V
On-chip Adc
6-chx10-bit
Instruction Set Architecture
RISC
Operating Temp Range
-40C to 85C
Operating Temperature Classification
Industrial
Mounting
Through Hole
Pin Count
28
Package Type
PDIP
Lead Free Status / Rohs Status
Compliant
19.8.3
8025K–AVR–10/09
Asynchronous Operational Range
Figure 19-7. 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 19-2 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
Table 19-2 on page 190
that can be tolerated. Note that Normal Speed mode has higher toleration of baud rate
variations.
F
M
slow
(U2X = 0)
(U2X = 1)
Sample
Sample
RxD
R
slow
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.
M
=
= 5 for Double Speed mode.
Figure
------------------------------------------ -
S 1
190) base frequency, the Receiver will not be able to synchronize the
1
1
(
and
D
+
2
19-7. For Double Speed mode the first low level must be delayed to
+
D S ⋅
1
Table 19-3 on page 190
)S
3
2
+
S
4
F
fast
5
3
is the ratio of the fastest incoming data rate that can be
6
7
4
8
STOP 1
9
5
ATmega48P/88P/168P
list the maximum receiver baud rate error
10
0/1
(A)
6
R
0/1
F
fast
= 8 for normal speed and S
M
0/1
0/1
(B)
= 9 for normal speed and
=
-----------------------------------
(
D
(
+
D
1
+
)S
2
)S
+
(C)
S
M
F
189
= 4

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