ATxmega256A3 Atmel Corporation, ATxmega256A3 Datasheet - Page 262

• 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

23.4.1
8077H–AVR–12/09
Key and State Memory
The following procedure for setup and use is recommended:
If more than one block is to be encrypted or decrypted repeat the procedure from step 3.
When the encryption/decryption procedure is complete the AES Interrupt Flag is set and the
optional interrupt is generated.
The AES Key and State memory are both 16 x 8-bit memories that are accessible through the
Key (KEY) and State (STATE) register, respectively.
Each memory has two 4-bit address pointers used to address the memory for read and write,
respectively. The initial value of the pointers are zero. After a read or write operation to the State
or Key register, the appropriate pointer is automatically incremented. Accessing (read or write)
the Control Register (CTRL) will reset all pointers to zero. A pointer overflow (a sequential read
or write is done more than 16 times) will also set the affected pointer to zero. The address point-
ers are not accessible from software. Read and write memory pointers are both incremented
during write operations in XOR mode.
Access to the Key and State registers are only possible when encryption/decryption is not in
progress.
Figure 23-2. The State memory with pointers and register
1. Enable AES interrupts (optional)
2. Select the AES direction, encryption or decryption.
3. Load the Key data block into the AES Key memory
4. Load the data block into the AES State memory
5. Start the encryption/decryption operation
address pointer
4-bit state write
reset or access
Reset pointer
to AES Control
I/O Data Bus
XOR
STATE
14
15
0
1
-
xor
STATE[read pointer]
address pointer
4-bit state read
reset or access
to AES Control
Reset pointer
XMEGA A
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