VDPVRAM.cc

Go to the documentation of this file.

#include "VDPVRAM.hh"
#include "SpriteChecker.hh"
#include "Renderer.hh"
#include "outer.hh"
#include "ranges.hh"
#include "serialize.hh"
#include <algorithm>
#include <array>
#include <bit>
 
namespace openmsx {
 
// class VRAMWindow
 
VRAMWindow::VRAMWindow(Ram& vram)
        : data(vram.data())
        // sizeMask will be initialized shortly by the VDPVRAM class
{
}
 
 
// class LogicalVRAMDebuggable
 
VDPVRAM::LogicalVRAMDebuggable::LogicalVRAMDebuggable(const VDP& vdp_)
        : SimpleDebuggable(vdp_.getMotherBoard(), vdp_.getName() == "VDP" ? "VRAM" :
                        vdp_.getName() + " VRAM",
                        "CPU view on video RAM given the current display mode.",
                         128 * 1024) // always 128kB
{
}
 
unsigned VDPVRAM::LogicalVRAMDebuggable::transform(unsigned address)
{
        auto& vram = OUTER(VDPVRAM, logicalVRAMDebug);
        return vram.vdp.getDisplayMode().isPlanar()
             ? ((address << 16) | (address >> 1)) & 0x1FFFF
             : address;
}
 
byte VDPVRAM::LogicalVRAMDebuggable::read(unsigned address, EmuTime::param time)
{
        auto& vram = OUTER(VDPVRAM, logicalVRAMDebug);
        return vram.cpuRead(transform(address), time);
}
 
void VDPVRAM::LogicalVRAMDebuggable::write(
        unsigned address, byte value, EmuTime::param time)
{
        auto& vram = OUTER(VDPVRAM, logicalVRAMDebug);
        vram.cpuWrite(transform(address), value, time);
}
 
 
// class PhysicalVRAMDebuggable
 
VDPVRAM::PhysicalVRAMDebuggable::PhysicalVRAMDebuggable(
                const VDP& vdp_, unsigned actualSize_)
        : SimpleDebuggable(vdp_.getMotherBoard(), vdp_.getName() == "VDP" ?
                           "physical VRAM" : strCat("physical ", vdp_.getName(), " VRAM"),
                           "VDP-screen-mode-independent view on the video RAM.",
                           actualSize_)
{
}
 
byte VDPVRAM::PhysicalVRAMDebuggable::read(unsigned address, EmuTime::param time)
{
        auto& vram = OUTER(VDPVRAM, physicalVRAMDebug);
        return vram.cpuRead(address, time);
}
 
void VDPVRAM::PhysicalVRAMDebuggable::write(
        unsigned address, byte value, EmuTime::param time)
{
        auto& vram = OUTER(VDPVRAM, physicalVRAMDebug);
        vram.cpuWrite(address, value, time);
}
 
 
// class VDPVRAM
 
static constexpr unsigned bufferSize(unsigned size)
{
        // Always allocate at least a buffer of 128kB, this makes the VR0/VR1
        // swapping a lot easier. Actually only in case there is also extended
        // VRAM, we need to allocate more.
        // TODO possible optimization: for TMS99x8 we could allocate 16kB, it
        //      has no VR modes.
        return std::max(0x20000u, size);
}
 
VDPVRAM::VDPVRAM(VDP& vdp_, unsigned size, EmuTime::param time)
        : vdp(vdp_)
        , data(*vdp_.getDeviceConfig2().getXML(), bufferSize(size))
        , logicalVRAMDebug (vdp)
        , physicalVRAMDebug(vdp, size)
        #ifdef DEBUG
        , vramTime(EmuTime::zero())
        #endif
        , actualSize(size)
        , vrMode(vdp.getVRMode())
        , cmdReadWindow(data)
        , cmdWriteWindow(data)
        , nameTable(data)
        , colorTable(data)
        , patternTable(data)
        , bitmapVisibleWindow(data)
        , bitmapCacheWindow(data)
        , spriteAttribTable(data)
        , spritePatternTable(data)
{
        setSizeMask(time);
 
        // Whole VRAM is cacheable.
        // Because this window has no observer, any EmuTime can be passed.
        // TODO: Move this to cache registration.
        bitmapCacheWindow.setMask(0x1FFFF, ~0u << 17, EmuTime::zero());
}
 
void VDPVRAM::clear()
{
        // Initialise VRAM data array.
        data.clear(0); // fill with zeros (unless initialContent is specified)
        if (data.size() != actualSize) {
                assert(data.size() > actualSize);
                // Read from unconnected VRAM returns random data.
                // TODO reading same location multiple times does not always
                // give the same value.
                ranges::fill(subspan(data, actualSize), 0xFF);
        }
}
 
void VDPVRAM::updateDisplayMode(DisplayMode mode, bool cmdBit, EmuTime::param time)
{
        assert(vdp.isInsideFrame(time));
        cmdEngine->updateDisplayMode(mode, cmdBit, time);
        renderer->updateDisplayMode(mode, time);
        spriteChecker->updateDisplayMode(mode, time);
}
 
void VDPVRAM::updateDisplayEnabled(bool enabled, EmuTime::param time)
{
        assert(vdp.isInsideFrame(time));
        cmdEngine->sync(time);
        renderer->updateDisplayEnabled(enabled, time);
        spriteChecker->updateDisplayEnabled(enabled, time);
}
 
void VDPVRAM::updateSpritesEnabled(bool enabled, EmuTime::param time)
{
        assert(vdp.isInsideFrame(time));
        cmdEngine->sync(time);
        renderer->updateSpritesEnabled(enabled, time);
        spriteChecker->updateSpritesEnabled(enabled, time);
}
 
void VDPVRAM::setSizeMask(EmuTime::param time)
{
        unsigned newSizeMask = (
                  vrMode
                // VR = 1: 64K address space, CAS0/1 is determined by A16
                ? (std::bit_ceil(actualSize) - 1) | (1u << 16)
                // VR = 0: 16K address space, CAS0/1 is determined by A14
                : (std::min(std::bit_ceil(actualSize), 0x4000u) - 1) | (1u << 14)
                ) | (1u << 17); // CASX (expansion RAM) is always relevant
 
        cmdReadWindow.setSizeMask(newSizeMask, time);
        cmdWriteWindow.setSizeMask(newSizeMask, time);
        nameTable.setSizeMask(newSizeMask, time);
        colorTable.setSizeMask(newSizeMask, time);
        patternTable.setSizeMask(newSizeMask, time);
        bitmapVisibleWindow.setSizeMask(newSizeMask, time);
        bitmapCacheWindow.setSizeMask(newSizeMask, time);
        spriteAttribTable.setSizeMask(newSizeMask, time);
        spritePatternTable.setSizeMask(newSizeMask, time);
 
        sizeMask = newSizeMask;
}
static constexpr unsigned swapAddr(unsigned x)
{
        // translate VR0 address to corresponding VR1 address
        //  note: output bit 0 is always 1
        //        input bit 6 is taken twice
        //        only 15 bits of the input are used
        return 1 | ((x & 0x007F) << 1) | ((x & 0x7FC0) << 2);
}
void VDPVRAM::updateVRMode(bool newVRmode, EmuTime::param time)
{
        if (vrMode == newVRmode) {
                // The swapping below may only happen when the mode is
                // actually changed. So this test is not only an optimization.
                return;
        }
        vrMode = newVRmode;
        setSizeMask(time);
 
        if (vrMode) {
                // switch from VR=0 to VR=1
                for (int i = 0x7FFF; i >=0; --i) {
                        std::swap(data[i], data[swapAddr(i)]);
                }
        } else {
                // switch from VR=1 to VR=0
                for (auto i : xrange(0x8000)) {
                        std::swap(data[i], data[swapAddr(i)]);
                }
        }
}
 
void VDPVRAM::setRenderer(Renderer* newRenderer, EmuTime::param time)
{
        renderer = newRenderer;
 
        bitmapVisibleWindow.resetObserver();
        // Set up bitmapVisibleWindow to full VRAM.
        // TODO: Have VDP/Renderer set the actual range.
        bitmapVisibleWindow.setMask(0x1FFFF, ~0u << 17, time);
        // TODO: If it is a good idea to send an initial sync,
        //       then call setObserver before setMask.
        bitmapVisibleWindow.setObserver(renderer);
}
 
void VDPVRAM::change4k8kMapping(bool mapping8k)
{
        /* Sources:
         *  - http://www.msx.org/forumtopicl8624.html
         *  - Charles MacDonald's sc3000h.txt (http://cgfm2.emuviews.com)
         *
         * Bit 7 of register #1 affects how the VDP generates addresses when
         * accessing VRAM. Here's a table illustrating the differences:
         *
         * VDP address      VRAM address
         * (Column)         4K mode     8/16K mode
         * AD0              VA0         VA0
         * AD1              VA1         VA1
         * AD2              VA2         VA2
         * AD3              VA3         VA3
         * AD4              VA4         VA4
         * AD5              VA5         VA5
         * AD6              VA12        VA6
         * AD7              Not used    Not used
         * (Row)
         * AD0              VA6         VA7
         * AD1              VA7         VA8
         * AD2              VA8         VA9
         * AD3              VA9         VA10
         * AD4              VA10        VA11
         * AD5              VA11        VA12
         * AD6              VA13        VA13
         * AD7              Not used    Not used
         *
         * ADx - TMS9928 8-bit VRAM address/data bus
         * VAx - 14-bit VRAM address that the VDP wants to access
         *
         * How the address is formed has to do with the physical layout of
         * memory cells in a DRAM chip. A 4Kx1 chip has 64x64 cells, a 8Kx1 or
         * 16Kx1 chip has 128x64 or 128x128 cells. Because the DRAM address bus
         * is multiplexed, this means 6 bits are used for 4K DRAMs and 7 bits
         * are used for 8K or 16K DRAMs.
         *
         * In 4K mode the 6 bits of the row and column are output first, with
         * the remaining high-order bits mapped to AD6. In 8/16K mode the 7
         * bits of the row and column are output normally. This also means that
         * even in 4K mode, all 16K of VRAM can be accessed. The only
         * difference is in what addresses are used to store data.
         */
        std::array<byte, 0x4000> tmp;
        if (mapping8k) {
                // from 8k/16k to 4k mapping
                for (unsigned addr8 = 0; addr8 < 0x4000; addr8 += 64) {
                        unsigned addr4 =  (addr8 & 0x203F) |
                                         ((addr8 & 0x1000) >> 6) |
                                         ((addr8 & 0x0FC0) << 1);
                        ranges::copy(subspan<64>(data, addr8),
                                     subspan<64>(tmp, addr4));
                }
        } else {
                // from 4k to 8k/16k mapping
                for (unsigned addr4 = 0; addr4 < 0x4000; addr4 += 64) {
                        unsigned addr8 =  (addr4 & 0x203F) |
                                         ((addr4 & 0x0040) << 6) |
                                         ((addr4 & 0x1F80) >> 1);
                        ranges::copy(subspan<64>(data, addr4),
                                     subspan<64>(tmp, addr8));
                }
        }
        //ranges::copy(tmp, std::span{data}); // TODO error with clang-15/libc++
        ranges::copy(tmp, std::span{data.begin(), data.end()});
}
 
 
template<typename Archive>
void VRAMWindow::serialize(Archive& ar, unsigned /*version*/)
{
        ar.serialize("baseAddr",  baseAddr,
                     "baseMask",  origBaseMask,
                     "indexMask", indexMask);
        if constexpr (Archive::IS_LOADER) {
                effectiveBaseMask = origBaseMask & sizeMask;
                combiMask = ~effectiveBaseMask | indexMask;
                // TODO ?  observer->updateWindow(isEnabled(), time);
        }
}
 
template<typename Archive>
void VDPVRAM::serialize(Archive& ar, unsigned /*version*/)
{
        if constexpr (Archive::IS_LOADER) {
                vrMode = vdp.getVRMode();
                setSizeMask(static_cast<MSXDevice&>(vdp).getCurrentTime());
        }
 
        ar.serialize_blob("data", std::span{data.data(), actualSize});
        ar.serialize("cmdReadWindow",       cmdReadWindow,
                     "cmdWriteWindow",      cmdWriteWindow,
                     "nameTable",           nameTable,
        // TODO: Find a way of changing the line below to "colorTable",
        // without breaking backwards compatibility
                     "colourTable",         colorTable,
                     "patternTable",        patternTable,
                     "bitmapVisibleWindow", bitmapVisibleWindow,
                     "bitmapCacheWindow",   bitmapCacheWindow,
                     "spriteAttribTable",   spriteAttribTable,
                     "spritePatternTable",  spritePatternTable);
}
INSTANTIATE_SERIALIZE_METHODS(VDPVRAM);
 
} // namespace openmsx