INES Mapper 226: Difference between revisions
From NESdev Wiki
Jump to navigationJump to search
(add a few details.) |
(links to various ICs) |
||
| (One intermediate revision by the same user not shown) | |||
| Line 1: | Line 1: | ||
[[Category:iNES Mappers | {{DEFAULTSORT:226}}[[Category:iNES Mappers]][[Category:Multicart mappers]][[Category:Discrete logic mappers]] | ||
Here are Disch's original notes: | Here are Disch's original notes: | ||
======================== | ======================== | ||
| Line 38: | Line 38: | ||
+---------------+---------------+ | +---------------+---------------+ | ||
The [http://nesdev.org/226.txt original describing document] states the 2s bit of the register at $8001 disables CHRRAM writes. No games seem to rely on it, though. It also says that the mapper hardware is made of a 74LS74A, 74LS273, 74LS139, 74LS02, and 74LS153. | The [http://nesdev.org/226.txt original describing document] states the 2s bit of the register at $8001 disables CHRRAM writes. No games seem to rely on it, though. It also says that the mapper hardware is made of a 74LS74A, 74LS273, [[74139|74LS139]], [[7402|74LS02]], and [[74153|74LS153]]. | ||
The multicart [http://web.archive.org/web/20030602133825/http://www.nesplayer.com/pirates/76in1.htm reportedly relies] on the value of uninitialized memory to determine exactly how many games are available. | The multicart [http://web.archive.org/web/20030602133825/http://www.nesplayer.com/pirates/76in1.htm reportedly relies] on the value of uninitialized memory to determine exactly how many games are available. | ||
Latest revision as of 01:32, 13 July 2017
Here are Disch's original notes:
========================
= Mapper 226 =
========================
Example Games:
--------------------------
76-in-1
Super 42-in-1
Registers:
---------------------------
Range, Mask: $8000-FFFF, $8001
$8000: [PMOP PPPP]
P = Low 6 bits of PRG Reg
M = Mirroring (0=Horz, 1=Vert)
O = PRG Mode
$8001: [.... ...H]
H = high bit of PRG
PRG Setup:
---------------------------
Low 6 bits of the PRG Reg come from $8000, high bit comes from $8001
$8000 $A000 $C000 $E000
+-------------------------------+
PRG Mode 0: | <Reg> |
+-------------------------------+
PRG Mode 1: | Reg | Reg |
+---------------+---------------+
The original describing document states the 2s bit of the register at $8001 disables CHRRAM writes. No games seem to rely on it, though. It also says that the mapper hardware is made of a 74LS74A, 74LS273, 74LS139, 74LS02, and 74LS153.
The multicart reportedly relies on the value of uninitialized memory to determine exactly how many games are available.
The multicart clears both registers on soft reset.
See also: Repair of one such cartridge
