Usbtiny has a protocol or firmware problem that prevents it from reading
flash above 64 kB in page mode (used by -U flash:r:... and -U flash✌️...).
This commit fixes that problem by falling back on byte access for flash paged
reads above 64k. It also issues the correct load extended address command for
parts with more than 128 kB flash thus extending support to ATmega2560 et al.
The paged read in pickit2.c has two errors:
- It drops load extended address commands unless a paged read happens at a
64k byte boundary; this is invalid when reading files with holes
- It wrongly assumed that flash memory is byte addressed
The fix is to carry out a load extended address command, if needed, at the
beginning of each paged flash read with the correct word address. Although the
pickit2_paged_load() has independent parameters page_size, addr and n_bytes,
AVRDUDE only ever calls paged read/write functions with page_size and n_bytes
both set to mem->page_size and addr aligned with a page boundary. Therefore, it
is sufficient to set the load extended address at the beginning of each page
read.
Stefan Rueger