I've observed some programs attempt to write to their character ROM area (that is PPU's $0000-$1FFFF address range) through $2007. Examples of this are "U-Force Test Cartridge (U)" or "1942 (JU)".
My question here is: as those writes cannot be made effective, how does a NES behave on this situation?
Thanks.
M.
I think that means that Micronics fails at programming.
On CHRROM boards, the pin CHR /WR is not connected, so writes to CHR ROM have absolutely no effect (they don't even make a bus conflict like writes to PRG ROM).
Heh, quite weird. Thanks for clarifying this.
I remember reading that some games write to CHR-ROM as a means of copy protection. If the write goes through, then the game refuses to run since it must be on a copier instead of a real cart.
dvdmth wrote:
I remember reading that some games write to CHR-ROM as a means of copy protection.
It worked for (earlier versions of) TuxNES.
What about $2002 D4? It is supposed to be "VRAM Write flag".. does it refer to nametables and such? Any game relying on this flag's behaviour?
Muchaserres wrote:
What about $2002 D4? It is supposed to be "VRAM Write flag".. does it refer to nametables and such? Any game relying on this flag's behaviour?
I believe that flag doesn't really exist, and $2002.4 always reads back as open bus. A goof in early documentation.