Connecting Atmel-ICE to a debugWIRE Target

The debugWIRE interface can not be used as a programming interface. This means that the SPI interface connection must also be available as shown “SPI Header Pinout” in order to program the target.

Although the debugWIRE interface only requires one signal line (RESET), Vcc and GND to operate correctly, it is advised to have access to the full SPI connector so that the debugWIRE interface can be enabled and disabled using SPI programming.

SPI Header Pinout

spi_header.png

When the debugWIRE enable fuse (DWEN) is set the SPI interface is overridden internally in order for the on-chip debugger (OCD) module to have control over the RESET pin. The debugWIRE OCD is capable of disabling itself temporarily (using the button on the debugging tab in the properties dialog in Atmel Studio), thus releasing control of the RESET line.

The SPI interface is then available again if the SPI enable fuse (SPIEN) is programmed allowing the DWEN fuse to be un-programmed using the SPI interface. If power is toggled before the DWEN fuse is un-programmed, the debugWIRE module will again take control of the RESET pin.

It is highly advised to simply let Atmel Studio handle setting and clearing of the DWEN fuse.

It is not possible to use the debugWIRE interface if the lockbits on the target AVR® device are programmed. Always be sure that the lockbits are cleared before programming the DWEN fuse and never set the lockbits while the DWEN fuse is programmed.

If both the DWEN fuse and lockbits are set, one can use High Voltage Programming to do a chip erase, and thus clear the lockbits.

When the lockbits are cleared the debugWIRE interface will be re-enabled. The SPI Interface is only capable of reading fuses, reading signature and performing a chip erase when the DWEN fuse is un-programmed.

Connection to a 6-pin 100-mil SPI header

Use the 6-pin 100-mil tap on the flat cable (included in some kits) to connect to a standard 100-mil SPI header.

Connection to a 6-pin 50-mil SPI header

Use the adapter board (included in some kits) to connect to a standard 50-mil SPI header.

Connection to a custom 100-mil header

The 10-pin mini-squid cable should be used to connect between the Atmel-ICE AVR connector port and the target board. Three connections are required, as described in Table: “Atmel-ICE debugWIRE Pin Mapping”.

Atmel-ICE debugWIRE Pin Mapping

debug_pinout.png
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