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75 lines
2.0 KiB
C++
75 lines
2.0 KiB
C++
//
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// DMADevice.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 14/09/2021.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#ifndef DMADevice_hpp
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#define DMADevice_hpp
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#include <array>
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#include <cstddef>
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#include <cstdint>
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#include "Flags.hpp"
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namespace Amiga {
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class Chipset;
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class DMADeviceBase {
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public:
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DMADeviceBase(Chipset &chipset, uint16_t *ram, size_t word_size) :
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chipset_(chipset), ram_(ram), ram_mask_(uint32_t(word_size - 1)) {}
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void posit_interrupt(Amiga::InterruptFlag::FlagT);
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protected:
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Chipset &chipset_;
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uint16_t *const ram_ = nullptr;
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const uint32_t ram_mask_ = 0;
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};
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template <size_t num_addresses, size_t num_modulos = 0> class DMADevice: public DMADeviceBase {
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public:
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using DMADeviceBase::DMADeviceBase;
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/// Writes the word @c value to the address register @c id, shifting it by @c shift (0 or 16) first.
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template <int id, int shift> void set_pointer(uint16_t value) {
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static_assert(id < num_addresses);
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static_assert(shift == 0 || shift == 16);
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byte_pointer_[id] = (byte_pointer_[id] & (0xffff'0000 >> shift)) | uint32_t(value << shift);
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pointer_[id] = byte_pointer_[id] >> 1;
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}
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/// Writes the word @c value to the modulo register @c id, shifting it by @c shift (0 or 16) first.
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template <int id> void set_modulo(uint16_t value) {
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static_assert(id < num_modulos);
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// Convert by sign extension.
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modulos_[id] = uint32_t(int16_t(value) >> 1);
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}
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template <int id, int shift> uint16_t get_pointer() {
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// Restore the original least-significant bit.
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const uint32_t source = (pointer_[id] << 1) | (byte_pointer_[id] & 1);
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return uint16_t(source >> shift);
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}
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protected:
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// These are shifted right one to provide word-indexing pointers;
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// subclasses should use e.g. ram_[pointer_[0] & ram_mask_] directly.
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std::array<uint32_t, num_addresses> pointer_{};
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std::array<uint32_t, num_modulos> modulos_{};
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private:
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std::array<uint32_t, num_addresses> byte_pointer_{};
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};
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}
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#endif /* DMADevice_hpp */
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