INES Mapper 072: Difference between revisions
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(tweaked m072 documentation a bit. no problem Lidnariq, keep it up.) |
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Commands pass through a latch. Rather than writing to the regs directly, you write the | |||
desired page number and command to the latch, then send another command that readies it for the next time. | desired page number and command to the latch, then send another command that readies it for the next time. | ||
| Line 42: | Line 42: | ||
Example: | Example: | ||
If a game wanted to select CHR page 3, it would first write $43, then $03. The $43 fills | If a game wanted to select CHR page 3, it would first write $43, then $03. The $43 fills the latch with command | ||
bits $4, which instruct bank $3 to be used for CHR; then the write of $03 prepares for the next write by | |||
resetting the command bits to $0. The $03 should be able to be any value from $00 to $0F, because the command | |||
bits are what is crucial. | |||
No current theory explains why games go to any effort to put the bank's nybble in the second byte, although perhaps it has to do with not disturbing the bank registers while the logic propagates. | No current theory explains why games go to any effort to put the bank's nybble in the second byte, although perhaps | ||
it has to do with not disturbing the bank registers while the logic propagates. | |||
CHR Setup: | CHR Setup: | ||
Revision as of 18:43, 13 June 2012
Note that Pinball Quest will require bus conflicts to be emulated if this mapper is emulated this way.
========================
= Mapper 072 =
========================
Example Games:
--------------------------
Pinball Quest (J)
Moero!! Pro Tennis
Moero!! Juudou Warriors
Registers (**BUS CONFLICTS**):
---------------------------
$8000-FFFF: [PCRS DDDD]
P = When a 1 is written after a 0 was previously written,
the bottom three bits of the data bus are copied to the PRG bank select
C = When a 1 is written after a 0 was previously written,
the bottom four bits of the data bus are copied to the CHR bank select
R = For games that have add-on sound, while 0,
the ADPCM playback IC is held in reset and unable to make sound
S = For games that have add-on sound, when the value written here changes
(direction unknown because the datasheet contradicts itself),
the sound specified by the bottom 5 bits of the address bus is played.
Leaving the value at 0 will probably result in erratic audio playback.
D = the three- or four- bit bank number to switch to, as appropriate.
Notes:
---------------------------
Commands pass through a latch. Rather than writing to the regs directly, you write the
desired page number and command to the latch, then send another command that readies it for the next time.
Commands (PC bits together):
%00 = Do nothing (prepare for next write)
%01 = Set CHR Page
%10 = Set PRG page
%11 = Set both simultaneously
Example:
If a game wanted to select CHR page 3, it would first write $43, then $03. The $43 fills the latch with command
bits $4, which instruct bank $3 to be used for CHR; then the write of $03 prepares for the next write by
resetting the command bits to $0. The $03 should be able to be any value from $00 to $0F, because the command
bits are what is crucial.
No current theory explains why games go to any effort to put the bank's nybble in the second byte, although perhaps
it has to do with not disturbing the bank registers while the logic propagates.
CHR Setup:
---------------------------
$0000 $0400 $0800 $0C00 $1000 $1400 $1800 $1C00
+---------------------------------------------------------------+
| CHR Reg |
+---------------------------------------------------------------+
PRG Setup:
---------------------------
$8000 $A000 $C000 $E000
+---------------+---------------+
| PRG Reg | { -1} |
+---------------+---------------+
