NES: Ignore consecutive reads to 4016/4017#185
Merged
Conversation
The NES (and AV Famicom) both ignore consecutive reads to 4016/4017 (when the reads on 2 consecutive CPU cycles). This implements that behavior when the corresponding console type is selected. These changes also simplify the DMA code, because a lot of extra code was in the DMA logic to simulate the same result. Moving this logic to the 4016/4017 reads makes the code simpler and allows it to work properly when a regular instruction reads from 4016/4017 twice in a row, too.
SourMesen
force-pushed
the
Sour4016DoubleRead
branch
from
e49bb8c to
7a11ec8
Compare
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
The NES (and AV Famicom) both ignore consecutive reads to 4016/4017 (when the reads on 2 consecutive CPU cycles). This implements that behavior when the corresponding console type is selected.
Also simplifies the DMA logic, because some of the DMA code existed only to simulate the same result. Moving this logic to the 4016/4017 reads makes the code simpler and allows it to work properly when a regular instruction reads from 4016/4017 twice in a row, too.