Use the PDI REPEAT instruction in the PDI programmer code to reduce protocol overhead and greatly improve transfer throughput. Switch bit-bang USART in the AVRISP project to Timer 1, so that Timer 0 can be used for hardware timeouts while waiting for the NVM bus or controller to become ready.

Fix NVM commands so that memory reads and CRC generations now work correctly using unoptimized PDI commands.

Split out NVM access code in the AVRISP project into a seperate NVMTarget.c source file and header. Make NVM register accesses use the NVM base address as set by the host, rather than using the fixed value from the XMEGA datasheet.