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282
8210C–AVR–09/11
Atmel AVR XMEGA D
Figure 23-1.
The PDI and PDI physical layers and closely related modules (grey).
23.3
PDI Physical
The PDI physical layer handles the low-level serial communication. It uses a bidirectional, half-
duplex, synchronous serial receiver and transmitter (just as a USART in USRT mode). The
physical layer includes start-of-frame detection, frame error detection, parity generation, parity
error detection, and collision detection.
In addition to PDI_CLK and PDI_DATA, the PDI_DATA pin has an internal pull resistor, V
CC
and
GND must be connected between the External Programmer/debugger and the device.
shows a typical connection.
Figure 23-2.
PDI connection.
The remainder of this section is intended for use only by third parties developing programmers
or programming support for Atmel AVR XMEGA devices.
23.3.1
Enabling
The PDI physical layer must be enabled before use. This is done by first forcing the PDI_DATA
line high for a period longer than the equivalent external reset minimum pulse width (refer to
device datasheet for external reset pulse width data). This will disable the RESET functionality of
the Reset pin, if not already disabled by the fuse settings.
PDI
Controller
PDI Physical
(physical layer)
OCD
NVM
Controller
Program and Debug Interface (PDI)
PDI_CLK
PDI_DATA
NVM
Memories
Internal Interfaces
PDIBUS
Connector
PDI_CLK
PDI_DATA
Vcc
Vcc