On 29/03/2018 16:34, Mia Magnusson wrote: > But no matter what it's not something an 8-bit wide rom should have to > deal with. For example there is no byte swapping when converting > between various file formats for eprom programmers, and of course the > contents of strings (with 8-bit chars) aren't byte swapped. When the 8088/6502/z80/(any little endian cpu) store the 16 bit value $aa55 will store it in an 8 bit rom as $55 $aa I regularly deal with roms that aren't mapped 1:1. Data and address lines can be swapped to simplify the routing on the pcb, which saves money and they can also be inverted. If you invert A0 then you will see similar effects to a 16 bit rom with the wrong endian. Finding ASCII in old roms is unusual, when so many systems (including commodore) stored text in a different scheme. One system I have been working on lately has $00-$09 as the digits "0"-"9" and $0a-$23 are the characters "A"-"Z" (which makes outputting hex really simple). Then it gets crazy as $2e-$48 are the letters "e"-"z" but characters with descenders ("g"/"j"/"p"/"q"/"y") take up two characters each. Then $49-$56 have the rest of the letters ("a"-"d") plus accented versions of "a"/"e"/"o"/"u". As there is zero context for where the rom comes from & we don't have the entire rom, then cutting down on what is possible is right next to impossible.Received on 2018-03-30 10:00:03
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