[bug #66044] core->dataAddressMask not applied correctly

[Georg-Johann Lay]

Follow-up Comment #1, bug #66044 (group simulavr):

Here is the respective clause from the "AVR Instruction Set Manual" at
https://ww1.microchip.com/downloads/en/DeviceDoc/AVR-InstructionSet-Manual-DS40002198.pdf

On page 87, section 6.66 LD - Load Indirect from Data Space to Register using
X:

6.66.1 Description
[...] Note that only the low byte of the X-pointer is updated
in devices with no more than 256 bytes of data space.
For such devices, the high byte of the pointer is not used
by this instruction and can be used for other purposes. [...]

Similar notes exist for the Y and Z registers.

The issue came up in an AVR-LibC test case, and there is also a proposed patch
for SimulAVR:
https://github.com/avrdudes/avr-libc/issues/954#issuecomment-2382476082



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