The ScreenConfiguration class

This class represents the configuration of the virtual machine’s screen.

Namespace: Spect.Net.SpectrumEmu.Devices.Screen
Assembly: Spect.Net.SpectrumEmu

public class ScreenConfiguration : IScreenConfiguration

The screen rendering mechanism uses a large number of configuration options that provides the timing so that the CPU and the rendering hardware can work in tandem. The software emulation implements the same mechanism.

As the following figure shows, the screen has visible and non-visible areas, just as in the case of the real hardware. Originally, the non-visible area was required by the cathode-ray tube so that the electron beam could sync the screen rendering properly.

ScreenWidth

public int ScreenWidth { get; }

The width of the visible screen area in pixels.

ScreenLines

public int ScreenLines { get; }

The height of the visible screen area in pixels.

DisplayWidth

public int DisplayWidth { get; }

The width of the display area in pixels (256).

DisplayLines

public int DisplayLines { get; }

The height of the display area in pixels.

NonVisibleBorderTopLines

public int NonVisibleBorderTopLines { get; }

The number of top border lines that are not visible when rendering the screen.

BorderTopLines

public int BorderTopLines { get; }

The number of border lines above the display area.

BorderBottomLines

public int BorderBottomLines { get; }

The number of border lines below the display area.

NonVisibleBorderBottomLines

public int NonVisibleBorderBottomLines { get; }

The number of bottom border lines that are not visible when rendering the screen.

VerticalSyncLines

public int VerticalSyncLines { get; }

Number of lines used for vertical synch.

BorderLeftTime

public int BorderLeftTime { get; }

The number of CPY T-cycles of displaying the left part of the border.

BorderLeftPixels

public int BorderLeftPixels { get; }

The number of border pixels to the left of the display (2 * BorderLeftTime).

BorderRightTime

public int BorderRightTime { get; }

The number of CPY T-cycles of displaying the right part of the border.

BorderRightPixels

public int BorderRightPixels { get; }

The number of border pixels to the right of the display (2 * BorderRightTime).

NonVisibleBorderRightTime

public int NonVisibleBorderRightTime { get; }

The time given in CPY T-cycles to render the nonvisible right part of the border.

HorizontalBlankingTime

public int HorizontalBlankingTime { get; }

Horizontal blanking time (HSync + blanking) given in CPU T-cycles.

The ScreenConfiguration class provides other properties that are related to screen rendering.

InterruptTact

public int InterruptTact { get; }

The tact index of the interrupt signal relative to the top-left screen pixel

FirstDisplayLine

public int FirstDisplayLine { get; }

The screen line number of the first display line (`VerticalSyncLines

• NonVisibleBorderTopLines + BorderTopLines`).

LastDisplayLine

public int LastDisplayLine { get; }

The screen line number of the last display line (FirstDisplayLine + DisplayLines - 1).

DisplayLineTime

public int DisplayLineTime { get; }

The time of rendering a display pixel row, given in CPU T-cycles.

ScreenLineTime

public int ScreenLineTime { get; }

The time of rendering an entire raster line, given in CPU T-cycles (BorderLeftTime + DisplayLineTime + BorderRightTime + NonVisibleBorderRightTime + HorizontalBlankingTime).

RasterLines

public int RasterLines { get; }

The number of raster lines in the screen (FirstDisplayLine + DisplayLines + BorderBottomLines + NonVisibleBorderBottomLines).

FirstDisplayPixelTact

public int FirstDisplayPixelTact { get; }

The tact in which the top left display pixel should be rendered, given in CPU T-cycles (FirstDisplayLine * ScreenLineTime + BorderLeftTime).

FirstScreenPixelTact

public int FirstScreenPixelTact { get; }

The tact in which the top left screen pixel (border) should be displayed ([VerticalSyncLines + NonVisibleBorderTopLines] * ScreenLineTime).

ScreenRenderingFrameTactCount

public int ScreenRenderingFrameTactCount { get; }

The number of CPU T-cycles used for the full rendering of the screen (RasterLines * ScreenLineTime).

Methods

The class provides a few helper methods.

IsTactVisible(int, int)

public bool IsTactVisible(int line, int tactInLine)

Tests whether the specified tact is in the visible area of the screen. Returns true, if the tact renders the visible part of the screen; otherwise, false.

Arguments

line: Raster line index
tactInLine: Tact index within the line

IsTactInDisplayArea(int, int)

public bool IsTactInDisplayArea(int line, int tactInLine)

Tests whether the specified tact is in the display area of the screen. Returns true, if the tact renders the display part of the screen; otherwise, false.

Arguments

line: Raster line index
tactInLine: Tact index within the line

The ScreenBitmap class

This class represents the current screen’s pixels, including the border. Every byte stands for a palette index. The value of a pixel can be #00 to #0F on a Spectrum 48K, 128K, and +3E model. On ZX Spectrum Next, the value is the entire byte range from #00 to #FF. The content is read-only, you cannot change it.

Namespace: Spect.Net.SpectrumEmu.Scripting
Assembly: Spect.Net.SpectrumEmu

public sealed class ScreenBitmap

this[int]

public byte[] this[int lineNo] { get; }

Retrieves a byte array for the raster line specified in lineNo. The value at zero index represent the leftmost border pixel of the line. The last item in the array is the rightmost pixel in the line.

this[int, int]

public byte this[int row, int column] { get; }

Retrieves the byte for the screen pixel in the given column of the specified row.

GetDisplayPixel(int, int)

public byte GetDisplayPixel(int row, int col)

While this[int, int] retrieves the specified screen pixel, this method obtains the display pixel of (row, column).

The ScreenRenderingStatus class

Provides properties about the current screen rendering status of the machine.

Namespace: Spect.Net.SpectrumEmu.Devices.Screen
Assembly: Spect.Net.SpectrumEmu

public sealed class ScreenRenderingStatus

CurrentFrameTact

public int CurrentFrameTact { get; }

Gets the number of the current tact within the frame being rendered.

RasterLine

public int RasterLine { get; }

Gets the number of the current raster line in the frame being rendered.

CurrentRenderingTact

public ScreenRenderingTact CurrentRenderingTact { get; }

Gets details about the current tact in the frame being rendered. See more details in the description of ScreenRenderingTact.

The ScreenRenderingTable class

Represents the screen rendering table of the virtual machine

Namespace: Spect.Net.SpectrumEmu.Devices.Screen
Assembly: Spect.Net.SpectrumEmu

public sealed class ScreenRenderingTable

Count

public int Count { get; }

Gets the number of items in the screen rendering table.

this[int]

public ScreenRenderingTact this[int index] { get; }

Gets the entry of the screen rendering table specified by index. See more details in the description of ScreenRenderingTact.

The ScreenRenderingTact class

Provides details about a screen rendering tact.

Namespace: Spect.Net.SpectrumEmu.Devices.Screen
Assembly: Spect.Net.SpectrumEmu

public sealed class ScreenRenderingTact

Phase

public ScreenRenderingPhase Phase { get; }

The rendering phase to be applied for the particular tact. The ScreenRenderingPhase enum has these values:

ContentionDelay

public byte ContentionDelay { get; }

Contention delay during the particular screen rendering tact, provided, the CPU is reading or writing data in the screen memory area (#4000-#7FFF).

PixelByteToFetchAddress

public ushort PixelByteToFetchAddress { get; }

Display memory address used in the particular tact to fetch the pixel value.

AttributeToFetchAddress

public ushort AttributeToFetchAddress { get; }

Display memory address used in the particular tact to fetch the attribute of a pixel.

XPos

public ushort XPos { get; }

The X position of the pixel in screen coordinates.

YPos

public ushort YPos { get; }

The Y position of the pixel in screen coordinates.