ATxmega256A3U Atmel Corporation, ATxmega256A3U Datasheet - Page 415

• Manufacturer Part Number: ATxmega256A3U
• Manufacturer: Atmel Corporation

Specifications of ATxmega256A3U

• 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 Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• 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

32.4
32.4.1
8331A–AVR–07/11
JTAG Physical
Enabling
Figure 32-8. Driving data out on the PDI_DATA using a bus keeper.
If the programmer and the PDI both drive the PDI_DATA line at the same time, drive contention
will occur, as illustrated in
clock cycles, the PDI is able to verify that the correct bit value is driven on the PDI_DATA line. If
the programmer is driving the PDI_DATA line to the opposite bit value to what the PDI expects,
a collision is detected.
Figure 32-9. Drive contention and collision detection on the PDI_DATA line.
As long as the PDI transmits alternating ones and zeros, collisions cannot be detected, because
the PDI output driver will be active all the time, preventing polling of the PDI_DATA line. How-
ever, the two stop bits should always be transmitted as ones within a single frame, enabling
collision detection at least once per frame.
The JTAG physical layer handles the basic low-level serial communication over four I/O lines,
TMS, TCK, TDI, and TDO. The JTAG physical layer includes BREAK detection, parity error
detection, and parity generation. For all generic JTAG details, refer to
Boundary Scan Interface” on page
The JTAGEN fuse must be programmed and the JTAG disable bit in the MCU control register
must be cleared to enable the JTAG interface. This is done by default. When the JTAG PDICOM
PDI_CLK
PDI Output
PDI_DATA
Programmer
Collision detect
Output enable
PDI Output
PDI_DATA
PDI_CLK
output
= Collision
1
1
Figure 32-9 on page
0
0
403.
X
1
415. Every time a bit value is kept for two or more
Atmel AVR XMEGA AU
1
1
0
X
0
”IEEE 1149.1 JTAG
1
1
1
415