6.2.3 aWire

The aWire interface makes use the /RESET wire of the Atmel AVR device to allow programming and debugging functions. A special enable sequence is transmitted by the Atmel AVR ONE!, which disables the default /RESET functionality of the pin.

When designing an application PCB, which includes an AVR with the aWire interface, it is recommended to use the pinout as shown in Figure 6-5. The AVR ONE! ships with both 100-mil and 50-mil adapters supporting this pinout.

Figure 6-5. aWire Header Pinout

Tip: Since aWire is a half-duplex interface, a pull-up resistor on the /RESET line in the order of 47k is recommended to avoid false start-bit detection when changing direction.

The aWire interface can be used as both a programming and debugging interface, all features of the OCD system available through the 10-pin JTAG interface can also be accessed using aWire.