ATmega3250A Atmel Corporation, ATmega3250A Datasheet - Page 187

• Manufacturer Part Number: ATmega3250A
• Manufacturer: Atmel Corporation

Specifications of ATmega3250A

• Flash (kbytes): 32 Kbytes
• Pin Count: 100
• Max. Operating Frequency: 20 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 69
• Ext Interrupts: 25
• Usb Speed: No
• Usb Interface: No
• Spi: 2
• Twi (i2c): 1
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 2
• Eeprom (bytes): 1024
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.8 to 5.5
• Operating Voltage (vcc): 1.8 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 3
• Output Compare Channels: 4
• Input Capture Channels: 1
• Pwm Channels: 4
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

8285D–AVR–06/11
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P
D
S
S
S
R
Table 20-2
that Normal Speed mode has higher toleration of baud rate variations.
Table 20-2.
Table 20-3.
The recommendations of the maximum receiver baud rate error was made under the assump-
tion that the Receiver and Transmitter equally divides the maximum total error.
There are two possible sources for the receivers baud rate error. The Receiver’s system clock
(XTAL) will always have some minor instability over the supply voltage range and the tempera-
ture range. When using a crystal to generate the system clock, this is rarely a problem, but for a
resonator the system clock may differ more than 2% depending of the resonators tolerance. The
second source for the error is more controllable. The baud rate generator can not always do an
F
M
slow
# (Data+Parity Bit)
# (Data+Parity Bit)
10
10
D
D
5
6
7
8
9
5
6
7
8
9
and
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.
Recommended Maximum Receiver Baud Rate Error for Normal Speed Mode
(U2Xn = 0)
Recommended Maximum Receiver Baud Rate Error for Double Speed Mode
(U2Xn = 1)
M
Table 20-3
= 5 for Double Speed mode.
R
R
slow
slow
93.20
94.12
94.81
95.36
95.81
96.17
94.12
94.92
95.52
96.00
96.39
96.70
list the maximum receiver baud rate error that can be tolerated. Note
(%)
(%)
fast
R
R
105.66
104.92
104,35
103.90
103.53
103.23
106.67
105.79
105.11
104.58
104.14
103.78
fast
fast
is the ratio of the fastest incoming data rate that can be
(%)
(%)
Max Total Error (%)
Max Total Error (%)
+5.66/-5.88
+4.92/-5.08
+4.35/-4.48
+3.90/-4.00
+3.53/-3.61
+3.23/-3.30
+5.79/-5.88
+5.11/-5.19
+4.58/-4.54
+4.14/-4.19
+3.78/-3.83
+6.67/-6.8
F
= 8 for normal speed and S
M
= 9 for normal speed and
Recommended Max
Recommended Max
Receiver Error (%)
Receiver Error (%)
± 2.5
± 2.0
± 1.5
± 1.5
± 1.5
± 1.0
± 3.0
± 2.5
± 2.0
± 2.0
± 1.5
± 1.5
F
187
= 4