62 lines
2.1 KiB
C++
62 lines
2.1 KiB
C++
/*
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Copyright 2016-2023 melonDS team
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This file is part of melonDS.
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melonDS is free software: you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation, either version 3 of the License, or (at your option)
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any later version.
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melonDS is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along
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with melonDS. If not, see http://www.gnu.org/licenses/.
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*/
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#ifndef DMA_TIMINGS_H
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#define DMA_TIMINGS_H
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#include <array>
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#include "types.h"
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namespace melonDS::DMATiming
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{
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// DMA timing tables
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//
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// DMA timings on the DS are normally straightforward, except in one case: when
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// main RAM is involved.
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// Main RAM to main RAM is the easy case: 16c/unit in 16bit mode, 18c/unit in 32bit
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// mode.
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// It gets more complicated when transferring from main RAM to somewhere else, or
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// vice versa: main RAM supports burst accesses, but the rules dictating how long
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// bursts can be are weird and inconsistent. Main RAM also supports parallel
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// memory operations, to some extent.
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// I haven't figured out the full logic behind it, let alone how to emulate it
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// efficiently, so for now we will use these tables.
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// A zero denotes the end of a burst pattern.
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//
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// Note: burst patterns only apply when the main RAM address is incrementing.
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// A fixed or decrementing address results in nonsequential accesses.
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//
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// Note about GBA slot/wifi timings: these take into account the sequential timing
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// setting. Timings are such that the nonseq setting only matters for the first
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// access, and minor edge cases (like the last of a 0x20000-byte block).
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extern const std::array<u8, 256> MRAMDummy;
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extern const std::array<u8, 256> MRAMRead16Bursts[3];
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extern const std::array<u8, 256> MRAMRead32Bursts[4];
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extern const std::array<u8, 256> MRAMWrite16Bursts[3];
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extern const std::array<u8, 256> MRAMWrite32Bursts[4];
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}
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#endif // DMA_TIMINGS_H
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