Fast video RAM for GLCD

[VCC]

Hi,
i wrote a simple video RAM for drawing lines on GLCD. Can somebody suggest improvements to make this faster?
If it matters, the code runs on dsPIC33EP512MC504.
Thank you

Code: Select all

var
  VirtualMem: array[1024] of Byte;

procedure ClearVirtualMem;
var
  i: Integer;
begin
  for i := 0 to 1023 do
    VirtualMem[i] := 0;
end;

procedure PutPixelOnVirtualMem(x, y: Integer; Color: Byte);
var
  i, yy: Word;
begin
  //i := x + ((y shr 3 ) and 7) shl 7;
  i := x + ((y and $0038) shl 4);
  if i > 1023 then
    i := 0; //Draw on 0,0 to display bugs

  yy := y and 7;  //position inside a byte
  VirtualMem[i].yy := Color;
end;

//line algorithm from http://members.chello.at/~easyfilter/Bresenham.pdf
procedure DrawLineOnVirtualMem(x0, y0, x1, y1: Integer; Color: Byte);  //Bresenham line on virtual RAM
var
  dx, dy, sx, sy, err, e2: Integer;
begin
  dx := Abs(x1 - x0);
  dy := - Abs(y1 - y0);

  if x0 < x1 then
    sx := 1
  else
    sx := -1;

  if y0 < y1 then
    sy := 1
  else
    sy := -1;

  err := dx + dy;

  repeat
    PutPixelOnVirtualMem(x0, y0, Color);
    if (x0 = x1) and (y0 = y1) then
      Break;

    e2 := err * 2;

    if e2 >= dy then
    begin
      err := err + dy;
      x0 := x0 + sx;
    end;

    if e2 <= dx then
    begin
      err := err + dx;
      y0 := y0 + sy;
    end;
  until False;
end;

procedure DrawVirtualMem;
var
  i, x, y, y7: Word;
begin
  Glcd_Set_Side(0); //Left side of the screen
  for y := 0 to 7 do
  begin
    y7 := y shl 7;
    Glcd_Set_Page(y);
    for x := 0 to 63 do
    begin
      Glcd_Set_X(x);
      i := x + y7;
      Glcd_Write_Data(VirtualMem[i]);
    end;
  end;

  Glcd_Set_Side(64); //Right side of the screen
  for y := 0 to 7 do
  begin
    y7 := y shl 7;
    Glcd_Set_Page(y);
    for x := 64 to 127 do
    begin
      Glcd_Set_X(x);
      i := x + y7;
      Glcd_Write_Data(VirtualMem[i]);
    end;
  end;
end;