ATXMEGA256A3B-MH Atmel, ATXMEGA256A3B-MH Datasheet - Page 238

• Manufacturer Part Number: ATXMEGA256A3B-MH
• Description: MCU AVR 256KB FLASH A3B 64-QFN
• Manufacturer: Atmel
• Series: AVR® XMEGAr

Specifications of ATXMEGA256A3B-MH

• Core Processor: AVR
• Core Size: 8/16-Bit
• Speed: 32MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, DMA, POR, PWM, WDT
• Number Of I /o: 49
• Program Memory Size: 256KB (128K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 4K x 8
• Ram Size: 16K x 8
• Voltage - Supply (vcc/vdd): 1.6 V ~ 3.6 V
• Data Converters: A/D 16x12b; D/A 2x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-MLF®, 64-QFN
• Processor Series: ATXMEGA256x
• Core: AVR8
• Data Bus Width: 8 bit, 16 bit
• Data Ram Size: 16 KB
• Interface Type: I2C, SPI, USART
• Maximum Clock Frequency: 32 MHz
• Number Of Programmable I/os: 49
• Number Of Timers: 7
• Operating Supply Voltage: 1.6 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: ATAVRDRAGON, ATAVRISP2, ATAVRONEKIT
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 12 bit, 8 Channel
• On-chip Dac: 12 bit, 2 Channel
• For Use With: ATAVRONEKIT - KIT AVR/AVR32 DEBUGGER/PROGRMMRATSTK600 - DEV KIT FOR AVR/AVR32770-1007 - ISP 4PORT ATMEL AVR MCU SPI/JTAG770-1004 - ISP 4PORT FOR ATMEL AVR MCU SPI
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ATXMEGA256A3B-MU; ATXMEGA256A3B-MU

Table 21-1.
Note:
21.3.2
21.3.3
8077H–AVR–12/09
Operating Mode
Asynchronous Normal
Speed mode (CLK2X = 0)
Asynchronous Double
Speed mode (CLK2X = 1)
Synchronous and SPI
Master mode
1. The baud rate is defined to be the transfer rate in bit per second (bps)
External Clock
Double Speed Operation (CLK2X)
Equations for Calculating Baud Rate Register Setting
External clock is used in synchronous slave mode operation. The XCK clock input is sampled on
the Peripheral Clock frequency (f
meta-stability. The output from the synchronization register is then passed through an edge
detector. This process introduces a delay of two peripheral clock periods, and therefore the max-
imum external XCK clock frequency (f
Each high and low period the XCK clock cycles must be sampled twice by the Peripheral Clock.
If the XCK clock has jitter, or the high/low period duty cycle is not 50/50, the maximum XCK
clock speed must be reduced accordingly.
Double Speed operation can be enabled to allow for higher baud rates on lower peripheral clock
frequencies under asynchronous operation. When Double Speed operation is enabled the baud
rate for a given asynchronous baud rate setting as shown in
bled. In this mode the Receiver will use half the number of samples (reduced from 16 to 8) for
data sampling and clock recovery. Due to the reduced sampling more accurate baud rate setting
and peripheral clock are required. See
243
f
XCK
Conditions
BSCALE ≥ 0
BSCALE < 0
BSCALE ≥ 0
BSCALE < 0
f
f
f
f
f
BAUD
BAUD
BAUD
BAUD
BAUD
for more details on accuracy.
<
f
---------- -
PER
4
≤
≤
≤
≤
<
f
---------- -
f
---------- -
f
---------- -
f
---------- -
f
---------- -
PER
PER
PER
PER
PER
16
16
8
8
2
f
f
BAUD
BAUD
f
f
BAUD
BAUD
Equation for Calculation
PER
=
=
f
=
BAUD
=
------------------------------------------------------------------ -
16((2
--------------------------------------------------------------- -
8((2
) by a synchronization register to minimize the chance of
XCK
Baud Rate
-------------------------------------------------------------- -
2
------------------------------------------------------------- -
2
BSCALE
BSCALE
Section 21.8 ”Asynchronous Data Reception” on page
BSCALE
)is limited by the following equation:
=
BSCALE
------------------------------------ -
2
⋅
⋅
f
(
⋅
f
PER
f
8
BSEL
f
PER
16(
PER
⋅
PER
(1)
f
⋅
⋅
PER
BSEL )
(
BSEL )
BSEL
BSEL
+
1
+
)
+
+
+
1)
1
1)
1)
)
Table 21-1 on page 238
BSEL
BSEL
BSEL
BSEL
Equation for Calculation
BSEL
=
=
=
=
---------------------
2
------------------------------------------------ 1
2
BSEL Value
---------------------
2
-------------------------------------------- - 1
2
BSCALE
BSCALE
BSCALE
BSCALE
1
=
1
XMEGA A
------------------ - 1
2f
f
f
f
BAUD
PER
PER
PER
⎛
⎝
⋅
⎛
⎝
--------------------- - 1
16f
⋅ f
16
------------------ - 1
8f
8
f
f
BAUD
PER
PER
f
BAUD
BAUD
will be dou-
BAUD
–
–
–
–
–
⎞
⎠
⎞
⎠
238