Disch wrote:
The bottom 2 rows of the attribute table are used when the attribute table is used as nametable data. So basically, it normally goes unused.
Attribute table's data become name table data when vertical scrooling value become negative (above 240), is that right ? So, what will hapend with mirroring (and wich color would be used on this data) ?
Is it impossible to write any vertical scrooling routine only based with attribute 4x4 blocks ? Because of the end of a nametable, a 4x4 block will have only it's half shown before the begining of the next name table, right ?
The only way to get arround this is to split a 4x4 block attribute data in two, and write the lower 4 bits to the bottom of name table 1, then the upper 4 bit to the top of nametalbe 1 if mirroring is vertical, name table 2 else. The hard thing would be to write those upper 4 bits and still have the old lowest 4 bits value to avoid gliches (exept if scrooling is horizontal, but the same problem would occur with horizontal scrooling and things get worst scince you have to break the 2 lowest and higest bits of both nybble in the attribute data). So, this algorithm can repat to the end of the following name table, then attribute lowest and higest nybble will be again together, it that right ?