Nonpareil status

[brouhaha]

The 12C self-test issue was definitely the C<>G instruction when pointer=13, as m-stgt commented in the issue on Github. I've changed Nonpareil to handle the pointer=13 case in the way the David Assembler ROM describes it, for the case where the pointer wasn't changed to 13 in the immediately previous cycle, and that seems to have fixed it.

There was a second problem with self-test, in the ON-divide keyboard and LCD test. Extraneous segments were being turned on. When I was first working on Voyager emulation in 2005, someone told me that in the display bitmap registers, which only have 50 bits rather than 56, that the low six bits read as the complement of bit 7 (though I'm not sure if they were counting from 0 or 1), and I put that in the Nonpareil code. Now I suspect that was not correct, as the display is wrong, but it's right if I have bits 0-5 always read as zero.

I'd like to hack a Voyager to execute my own code to investigate the bitmap register issue further, and also to understand the hardware register 8 behavior, but I'm not sure when I'll find time to do that.