In certain situations (CRC failure, device locked), that JTAG3
read functions need to return an indication to the caller that
it is OK to proceed, and allow erasing the device anyway.
Historically, the JTAG3 code passed the respective protocol
errors directly (and unexplained) up to the caller, leaving
the decision to the caller how to handle the situation.
Replace that by a more common return value API. New code should
prefer this API instead of any hardcoded return values.
This feature has been designed with the sometimes quite flakey direct
(parallel or serial port attached) bitbang programming adapters in
mind that were quite common about two decades ago.
With parallel ports vanishing from modern PCs almost completely, and
the advent of various USB-attached low-cost programming devices,
this class of programmers disappeared almost completely.
Furthermore, the fuse combinations that were covered by the feature
are no longer around on all recent AVR devices, so for an ever
increasing number of devices, safemode already became meaningless and
was turned off anyway.
With the prospective version 7.x release, it's a good point in time to
introduce a major change like this one.
In get_fuse_bitmask(), ensure the AVR_OP_READ and AVR_OP_WRITE
m->op[] fields are actually filled in, before referencing them.
If they are missing, just return a full byte mask (0xFF).
In avr_write(), for TPI memory, if the write consist of one byte onle
(which is the case for fuse byte writing), resort to avr_write_byte()
instead as it already implements everything needed. This leaves the
avr_write() implementation to handle full paged writes with an even
number of bytes only.
Stefan Rueger
Joerg Wunsch
Stefan Rueger
Marius Greuel