NES 2.0 Mapper 328

From Nesdev wiki
Jump to: navigation, search

NES 2.0 mapper 328 is used for the Test Ver. 1.01 Dlya Proverki TV Pristavok test cartridge. Its UNIF board name is UNL-RT-01. There is only 16K of PRG and 2K of CHR and mirroring is hard-wired.

Random number generator or Protection ($CE80-$CEFF, $FE80-$FEFF, read)

Mask: unknown. If what CaH4e3 wrote (quoted below) is accurate, $BFFF.

D~7654 3210
  ---------
  1111 RR1R
       ++-+- Random bits

CaH4e3 wrote that the "PRG EPROM has copy protected areas with "weak bits", which is tested at some points of the program. [The random numbers are t]rying to simulate "weak bits" behaviour"

The relevant program calculates a 16-bit checksum of the memory in each of these regions and loops until the checksum changes.