The initial implementation was testing the byte value rather than
the converted value, so backslashes were getting through in high
ASCII strings. PETSCII and C64 screen codes don't really have a
backslash so it's not really an issue there.
The new implementation handles high ASCII correctly. The various
201n0-char-encoding-x regression tests have been updated to verify
this.
We have a single character-encoding test that is cloned 3x so we can
exercise the different values for the project's default character
set. It was a 65816 test because it tested 16-bit immediate char
operands, but that's a very small part of it.
The 65816-specific portion is now 20122-char-encoding. The rest is
now 201{2,3,4}0-char-encoding-X.
