ATxmega256A3 Atmel Corporation, ATxmega256A3 Datasheet - Page 221

• Manufacturer Part Number: ATxmega256A3
• Manufacturer: Atmel Corporation

Specifications of ATxmega256A3

• Flash (kbytes): 256 Kbytes
• Pin Count: 64
• Max. Operating Frequency: 32 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 50
• Ext Interrupts: 50
• Usb Speed: No
• Usb Interface: No
• Spi: 10
• Twi (i2c): 2
• Uart: 7
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 16
• Adc Resolution (bits): 12
• Adc Speed (ksps): 2000
• Analog Comparators: 4
• Resistive Touch Screen: No
• Dac Channels: 2
• Dac Resolution (bits): 12
• Temp. Sensor: Yes
• Crypto Engine: AES/DES
• Sram (kbytes): 16
• Eeprom (bytes): 4096
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: Yes
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 1.6 to 3.6
• Operating Voltage (vcc): 1.6 to 3.6
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 7
• Output Compare Channels: 22
• Input Capture Channels: 22
• Pwm Channels: 22
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

19.9.5
8077H–AVR–12/09
BAUD - TWI Baud Rate Register
• Bit 2 - BUSERR: Bus Error
The Bus Error (BUSERR) flag is set if an illegal bus condition has occurred. An illegal bus condi-
tion occurs if a Repeated START or STOP condition is detected, and the number of bits from the
previous START condition is not a multiple of nine. Writing a one to this bit location will clear the
BUSERR flag.
Writing the ADDR register will automatically clear the BUSERR flag.
• Bit 1:0 - BUSSTATE[1:0]: Bus State
The Bus State (BUSSTATE) bits indicate the current TWI bus state as defined in
The change of bus state is dependent on bus activity. Refer to the
Logic” on page
Table 19-5.
Writing 01 to the BUSSTATE bits forces the bus state logic into idle state. The bus state logic
cannot be forced into any other state. When the master is disabled, and after reset the Bus State
logic is disabled and the bus state is unknown.
The Baud Rate (BAUD) register defines the relation between the system clock and the TWI Bus
Clock (SCL) frequency. The frequency relation can be expressed by using the following
equation:
The BAUD register must be set to a value that results in a TWI bus clock frequency (f
or less 100 kHz or 400 kHz dependent on standard used by the application. The following equa-
tion [2] expresses equation [1] with respect to the BAUD value:
The BAUD register should be written while the master is disabled.
f
TWMBR
TWI
Bit
+0x04
Read/Write
Initial Value
=
BUSSTATE[1:0]
--------------------------------------- - [Hz]
2(5
=
+
------------- - 5
2f
00
01
10
11
f
TWMBR)
f
sys
TWI
sys
R/W
7
0
TWI master Bus State
212.
–
[2]
R/W
6
0
[1]
Group Configuration
UNKNOWN
R/W
5
0
OWNER
BUSY
IDLE
R/W
4
0
BAUD[7:0]
R/W
Description
Unknown Bus State
Idle
Owner
Busy
3
0
R/W
2
0
Section 19.4 ”TWI Bus State
R/W
1
0
XMEGA A
R/W
0
0
Table
TWI
) equal
BAUD
19-5.
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