The description of the wiki is correct but not brief. I simplified and optimized the logic, and now the readability and logic are very clear, and the implementation is also simpler:Now, mapper451 can share implementation logic with mapper471, and I claim that mapper471 is a subset of mapper451
Just need modify a little, the first 16x8K banks should be filled with bank $0, and the last 16x8K banks filled with bank $30.
It is similar to adding scanline based IRQ to gxrom/bxrom, and the overdumped ROM can be reduced to 1/4 size
Code:
Bank Register ($E000-$FFFF)A~[111. .... .... ..BA] |+- PRG/CHR A13 +-- PRG A16prg_addr_out[18:13] = {cpu_addr_in[14:13], reg_e000[1], 2'b00, reg_e000[0]};chr_addr_out[13] = reg_e000[0];Just need modify a little, the first 16x8K banks should be filled with bank $0, and the last 16x8K banks filled with bank $30.
It is similar to adding scanline based IRQ to gxrom/bxrom, and the overdumped ROM can be reduced to 1/4 size
Statistics: Posted by aquasnake — Fri Apr 05, 2024 12:53 am — Replies 0 — Views 44
