ATMEGA64-16AJ Atmel, ATMEGA64-16AJ Datasheet - Page 185
![IC MCU AVR 64K 5V 16MHZ 64-TQFP](/photos/12/13/121332/313-64-tqfp_sml.jpg)
ATMEGA64-16AJ
Manufacturer Part Number
ATMEGA64-16AJ
Description
IC MCU AVR 64K 5V 16MHZ 64-TQFP
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA64-16AJ
Core Processor
AVR
Core Size
8-Bit
Speed
16MHz
Connectivity
I²C, SPI, UART/USART
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
53
Program Memory Size
64KB (32K x 16)
Program Memory Type
FLASH
Eeprom Size
2K x 8
Ram Size
4K x 8
Voltage - Supply (vcc/vdd)
4.5 V ~ 5.5 V
Data Converters
A/D 8x10b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
64-TQFP, 64-VQFP
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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Asynchronous Data
Recovery
2490Q–AVR–06/10
the figure. The Clock Recovery logic then uses samples 8, 9 and 10 for Normal mode, and sam-
ples 4, 5 and 6 for Double Speed mode (indicated with sample numbers inside boxes on the
figure), to decide if a valid start bit is received. If two or more of these three samples have logical
high levels (the majority wins), the start bit is rejected as a noise spike and the Receiver starts
looking for the next high to low-transition. If however, a valid start bit is detected, the clock recov-
ery logic is synchronized and the data recovery can begin. The synchronization process is
repeated for each start bit.
When the receiver clock is synchronized to the start bit, the data recovery can begin. The data
recovery unit uses a state machine that has 16 states for each bit in Normal mode and eight
states for each bit in Double Speed mode.
parity bit. Each of the samples is given a number that is equal to the state of the recovery unit.
Figure 84. Sampling of Data and Parity Bit
The decision of the logic level of the received bit is taken by doing a majority voting of the logic
value to the three samples in the center of the received bit. The center samples are emphasized
on the figure by having the sample number inside boxes. The majority voting process is done as
follows: If two or all three samples have high levels, the received bit is registered to be a logic 1.
If two or all three samples have low levels, the received bit is registered to be a logic 0. This
majority voting process acts as a low pass filter for the incoming signal on the RxD pin. The
recovery process is then repeated until a complete frame is received. Including the first stop bit.
Note that the receiver only uses the first stop bit of a frame.
stop bit and the earliest possible beginning of the start bit of the next frame.
Figure 85. 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 n (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
(C) marks a stop bit of full length. The early start bit detection influences the operational range of
the Receiver.
(U2X = 0)
(U2X = 1)
(U2X = 0)
(U2X = 1)
Sample
Sample
Sample
Sample
RxD
RxD
Figure
1
1
1
1
2
2
85. For Double Speed mode the first low level must be delayed to (B).
3
2
3
2
4
4
5
3
5
3
6
6
Figure 84
7
4
7
4
8
8
STOP 1
BIT n
9
5
9
5
shows the sampling of the data bits and the
10
10
(A)
0/1
11
6
6
Figure 85
0/1
12
(B)
0/1
0/1
13
7
shows the sampling of the
14
ATmega64(L)
15
8
16
(C)
1
1
185
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