ATxmega16D4 Atmel Corporation, ATxmega16D4 Datasheet - Page 262

• Manufacturer Part Number: ATxmega16D4
• Manufacturer: Atmel Corporation

Specifications of ATxmega16D4

• Flash (kbytes): 16 Kbytes
• Pin Count: 44
• Max. Operating Frequency: 32 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 34
• Ext Interrupts: 34
• Usb Speed: No
• Usb Interface: No
• Spi: 4
• Twi (i2c): 2
• Uart: 2
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 12
• Adc Resolution (bits): 12
• Adc Speed (ksps): 200
• Analog Comparators: 2
• Resistive Touch Screen: No
• Temp. Sensor: Yes
• Crypto Engine: No
• Sram (kbytes): 2
• Eeprom (bytes): 1024
• 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: 4
• Output Compare Channels: 14
• Input Capture Channels: 14
• Pwm Channels: 14
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

22.3.5.1
8210B–AVR–04/10
Drive contention and collision detection
In order to reduce the effect of a drive contention (the PDI and the programmer drives the
PDI_DATA line at the same time), a mechanism for collision detection is supported. The mecha-
nism is based on the way the PDI drives data out on the PDI_DATA line. As shown in Figure 7,
the output pin driver is only active when the output value changes (from 0-1 or 1-0). Hence, if
two or more successive bit values are the same, the value is only actively driven the first clock
cycle. After this point the output driver is automatically tri-stated, and the PDI_DATA pin has a
bus-keeper responsible for keeping the pin-value unchanged until the output driver is re-enabled
due to a bit value change.
Figure 22-7. Driving data out on the PDI_DATA using bus-keeper
If the programmer and the PDI both drives the PDI_DATA line at the same time, the situation of
drive contention will occur as illustrated in
kept for two or more 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
than what the PDI expects, a collision is detected.
Figure 22-8. 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 output driver will be active all the time preventing polling of the PDI_DATA line. However,
within a single frame the two stop bits should always be transmitted as ones, enabling collision
detection at least once per frame.
Output enable
Programmer
Driven output
PDI output
PDI_CLK
PDI_DATA
Collision
PDI_CLK
PDI_DATA
output
detect
= Collision
1
1
0
0
Figure 22-8 on page
X
1
1
1
X
0
262. Every time a bit value is
1
0
XMEGA D
1
1
262