ATMEGA128RFA1-ZU Atmel, ATMEGA128RFA1-ZU Datasheet - Page 184

IC AVR MCU 2.4GHZ XCEIVER 64QFN

ATMEGA128RFA1-ZU

Manufacturer Part Number
ATMEGA128RFA1-ZU
Description
IC AVR MCU 2.4GHZ XCEIVER 64QFN
Manufacturer
Atmel
Series
ATMEGAr

Specifications of ATMEGA128RFA1-ZU

Frequency
2.4GHz
Data Rate - Maximum
2Mbps
Modulation Or Protocol
802.15.4 Zigbee
Applications
General Purpose
Power - Output
3.5dBm
Sensitivity
-100dBm
Voltage - Supply
1.8 V ~ 3.6 V
Current - Receiving
12.5mA
Current - Transmitting
14.5mA
Data Interface
PCB, Surface Mount
Memory Size
128kB Flash, 4kB EEPROM, 16kB RAM
Antenna Connector
PCB, Surface Mount
Operating Temperature
-40°C ~ 85°C
Package / Case
64-VFQFN, Exposed Pad
Rf Ic Case Style
QFN
No. Of Pins
64
Supply Voltage Range
1.8V To 3.6V
Operating Temperature Range
-40°C To +85°C
Svhc
No SVHC (15-Dec-2010)
Rohs Compliant
Yes
Processor Series
ATMEGA128x
Core
AVR8
Data Bus Width
8 bit
Program Memory Type
Flash
Program Memory Size
128 KB
Data Ram Size
16 KB
Interface Type
JTAG
Maximum Clock Frequency
16 MHz
Number Of Programmable I/os
38
Number Of Timers
6
Operating Supply Voltage
1.8 V to 3.6 V
Maximum Operating Temperature
+ 85 C
Mounting Style
SMD/SMT
3rd Party Development Tools
EWAVR, EWAVR-BL
Development Tools By Supplier
ATAVR128RFA1-EK1
Lead Free Status / RoHS Status
Lead free / RoHS Compliant

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Asynchronous Clock
Recovery
Asynchronous Data
Recovery
184
ATmega128
The clock recovery logic synchronizes internal clock to the incoming serial frames.
illustrates the sampling process of the start bit of an incoming frame. The sample rate is 16 times
the baud rate for normal mode, and 8 times the baud rate for Double Speed mode. The horizon-
tal arrows illustrate the synchronization variation due to the sampling process. Note the larger
time variation when using the double speed mode (U2X = 1) of operation. Samples denoted zero
are samples done when the RxD line is idle (i.e., no communication activity).
Figure 83. Start Bit Sampling
When the clock recovery logic detects a high (idle) to low (start) transition on the RxD line, the
start bit detection sequence is initiated. Let sample 1 denote the first zero-sample as shown in
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 8 states
for each bit in Double Speed mode.
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.
(U2X = 0)
(U2X = 1)
(U2X = 0)
(U2X = 1)
Sample
Sample
Sample
Sample
RxD
RxD
0
0
IDLE
0
1
1
1
1
2
2
3
2
3
2
4
4
Figure 84
5
3
5
3
6
6
7
7
4
4
shows the sampling of the data bits and the parity
8
8
START
BIT n
9
5
9
5
10
10
11
11
6
6
Figure 85
12
12
13
13
7
7
shows the sampling of the
14
14
15
15
8
8
16
16
1
1
1
1
2467V–AVR–02/11
2
BIT 0
Figure 83
3
2

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