nds specifications.htm

工程技术文档：NDS游戏机系统描述文档（英文版）

  <TR>
    <TD><PRE>  Bit   Expl.
  0-7   Fractional portion (8 bits)
  8-26  Integer portion    (19 bits)
  27    Sign               (1 bit)
  28-31 Not used
</PRE></TD></TR></TBODY></TABLE>Because values are shifted left by eight, 
fractional portions may be specified in steps of 1/256 pixels (this would be 
relevant only if the screen is actually rotated or scaled). Normal signed 32bit 
values may be written to above registers (the most significant bits will be 
ignored and the value will be cut-down to 28bits, but this is no actual problem 
because signed values have set all MSBs to the same value).<BR><BR><B>Internal 
Reference Point Registers</B><BR>The above reference points are automatically 
copied to internal registers during each vblank, specifying the origin for the 
first scanline. The internal registers are then incremented by dmx and dmy after 
each scanline.<BR>Caution: Writing to a reference point register by software 
outside of the Vblank period does immediately copy the new value to the 
corresponding internal register, that means: in the current frame, the new value 
specifies the origin of the &lt;current&gt; scanline (instead of the topmost 
scanline).<BR><BR><B>4000020h - BG2PA - BG2 Rotation/Scaling Parameter A (alias 
dx) (W)</B><BR><B>4000022h - BG2PB - BG2 Rotation/Scaling Parameter B (alias 
dmx) (W)</B><BR><B>4000024h - BG2PC - BG2 Rotation/Scaling Parameter C (alias 
dy) (W)</B><BR><B>4000026h - BG2PD - BG2 Rotation/Scaling Parameter D (alias 
dmy) (W)</B><BR>
<TABLE>
  <TBODY>
  <TR>
    <TD><PRE>  Bit   Expl.
  0-7   Fractional portion (8 bits)
  8-14  Integer portion    (7 bits)
  15    Sign               (1 bit)
</PRE></TD></TR></TBODY></TABLE>See below for details.<BR><BR><B>400003Xh - 
BG3X_L/H, BG3Y_L/H, BG3PA-D - BG3 Rotation/Scaling Parameters</B><BR>Same as 
above BG2 Reference Point, and Rotation/Scaling Parameters, for BG3 
respectively.<BR><BR><B>dx (PA) and dy (PC)</B><BR>When transforming a 
horizontal line, dx and dy specify the resulting gradient and magnification for 
that line. For example:<BR>Horizontal line, length=100, dx=1, and dy=1. The 
resulting line would be drawn at 45 degrees, f(y)=1/1*x. Note that this would 
involve that line is magnified, the new length is SQR(100^2+100^2)=141.42. Yup, 
exactly - that's the old a^2 + b^2 = c^2 formula.<BR><BR><B>dmx (PB) and dmy 
(PD)</B><BR>These values define the resulting gradient and magnification for 
transformation of vertical lines. However, when rotating a square area (which is 
surrounded by horizontal and vertical lines), then the desired result should be 
usually a rotated &lt;square&gt; area (ie. not a parallelogram, for 
example).<BR>Thus, dmx and dmy must be defined in direct relationship to dx and 
dy, taking the example above, we'd have to set dmx=-1, and dmy=1, 
f(x)=-1/1*y.<BR><BR><B>Area Overflow</B><BR>In result of rotation/scaling it may 
often happen that areas outside of the actual BG area become moved into the LCD 
viewport. Depending of the Area Overflow bit (BG2CNT and BG3CNT, Bit 13) these 
areas may be either displayed (by wrapping the BG area), or may be displayed 
transparent.<BR>This works only in BG modes 1 and 2. The area overflow is 
ignored in Bitmap modes (BG modes 3-5), the outside of the Bitmaps is always 
transparent.<BR><BR>--- more details and confusing or helpful formulas 
---<BR><BR><B>The following parameters are required for Rotation/Scaling</B><BR>
<TABLE>
  <TBODY>
  <TR>
    <TD><PRE>  Rotation Center X and Y Coordinates (x0,y0)
  Rotation Angle                      (alpha)
  Magnification X and Y Values        (xMag,yMag)
</PRE></TD></TR></TBODY></TABLE>The display is rotated by 'alpha' degrees around 
the center.<BR>The displayed picture is magnified by 'xMag' along x-Axis (Y=y0) 
and 'yMag' along y-Axis (X=x0).<BR><BR><B>Calculating Rotation/Scaling 
Parameters A-D</B><BR>
<TABLE>
  <TBODY>
  <TR>
    <TD><PRE>  A = Cos (alpha) / xMag    ;distance moved in direction x, same line
  B = Sin (alpha) / xMag    ;distance moved in direction x, next line
  C = Sin (alpha) / yMag    ;distance moved in direction y, same line
  D = Cos (alpha) / yMag    ;distance moved in direction y, next line
</PRE></TD></TR></TBODY></TABLE><BR><B>Calculating the position of a 
rotated/scaled dot</B><BR>Using the following expressions,<BR>
<TABLE>
  <TBODY>
  <TR>
    <TD><PRE>  x0,y0    Rotation Center
  x1,y1    Old Position of a pixel (before rotation/scaling)
  x2,y2    New position of above pixel (after rotation scaling)
  A,B,C,D  BG2PA-BG2PD Parameters (as calculated above)
</PRE></TD></TR></TBODY></TABLE>the following formula can be used to calculate 
x2,y2:<BR>
<TABLE>
  <TBODY>
  <TR>
    <TD><PRE>  x2 = A(x1-x0) + B(y1-y0) + x0
  y2 = C(x1-x0) + D(y1-y0) + y0
</PRE></TD></TR></TBODY></TABLE><BR><BR>
<TABLE width="100%">
  <TBODY>
  <TR bgColor=#cccccc>
    <TD><A name=lcdiowindowfeature></A><FONT size=+2>&nbsp;LCD I/O Window 
      Feature</FONT></TD></TR></TBODY></TABLE><BR>The Window Feature may be used to 
split the screen into four regions. The BG0-3,OBJ layers and Color Special 
Effects can be separately enabled or disabled in each of these 
regions.<BR><BR><B>The DISPCNT Register</B><BR>DISPCNT Bits 13-15 are used to 
enable Window 0, Window 1, and/or OBJ Window regions, if any of these regions is 
enabled then the "Outside of Windows" region is automatically enabled, 
too.<BR>DISPCNT Bits 8-12 are kept used as master enable bits for the BG0-3,OBJ 
layers, a layer is displayed only if both DISPCNT and WININ/OUT enable bits are 
set.<BR><BR><B>4000040h - WIN0H - Window 0 Horizontal Dimensions 
(W)</B><BR><B>4000042h - WIN1H - Window 1 Horizontal Dimensions (W)</B><BR>
<TABLE>
  <TBODY>
  <TR>
    <TD><PRE>  Bit   Expl.
  0-7   X2, Rightmost coordinate of window, plus 1
  8-15  X1, Leftmost coordinate of window
</PRE></TD></TR></TBODY></TABLE>Garbage values of X2&gt;240 or X1&gt;X2 are 
interpreted as X2=240.<BR><BR><B>4000044h - WIN0V - Window 0 Vertical Dimensions 
(W)</B><BR><B>4000046h - WIN1V - Window 1 Vertical Dimensions (W)</B><BR>
<TABLE>
  <TBODY>
  <TR>
    <TD><PRE>  Bit   Expl.
  0-7   Y2, Bottom-most coordinate of window, plus 1
  8-15  Y1, Top-most coordinate of window
</PRE></TD></TR></TBODY></TABLE>Garbage values of Y2&gt;160 or Y1&gt;Y2 are 
interpreted as Y2=160.<BR><BR><B>4000048h - WININ - Control of Inside of 
Window(s) (R/W)</B><BR>
<TABLE>
  <TBODY>
  <TR>
    <TD><PRE>  Bit   Expl.
  0-3   Window 0 BG0-BG3 Enable Bits     (0=No Display, 1=Display)
  4     Window 0 OBJ Enable Bit          (0=No Display, 1=Display)
  5     Window 0 Color Special Effect    (0=Disable, 1=Enable)
  6-7   Not used
  8-11  Window 1 BG0-BG3 Enable Bits     (0=No Display, 1=Display)
  12    Window 1 OBJ Enable Bit          (0=No Display, 1=Display)
  13    Window 1 Color Special Effect    (0=Disable, 1=Enable)
  14-15 Not used
</PRE></TD></TR></TBODY></TABLE><BR><B>400004Ah - WINOUT - Control of Outside of 
Windows &amp; Inside of OBJ Window (R/W)</B><BR>
<TABLE>
  <TBODY>
  <TR>
    <TD><PRE>  Bit   Expl.
  0-3   Outside BG0-BG3 Enable Bits      (0=No Display, 1=Display)
  4     Outside OBJ Enable Bit           (0=No Display, 1=Display)
  5     Outside Color Special Effect     (0=Disable, 1=Enable)
  6-7   Not used
  8-11  OBJ Window BG0-BG3 Enable Bits   (0=No Display, 1=Display)
  12    OBJ Window OBJ Enable Bit        (0=No Display, 1=Display)
  13    OBJ Window Color Special Effect  (0=Disable, 1=Enable)
  14-15 Not used
</PRE></TD></TR></TBODY></TABLE><BR><B>The OBJ Window</B><BR>The dimension of 
the OBJ Window is specified by OBJs which are having the "OBJ Mode" attribute 
being set to "OBJ Window". Any non-transparent dots of any such OBJs are marked 
as OBJ Window area. The OBJ itself is not displayed.<BR>The color, palette, and 
display priority of these OBJs are ignored. Both DISPCNT Bits 12 and 15 must be 
set when defining OBJ Window region(s).<BR><BR><B>Window Priority</B><BR>In case 
that more than one window is enabled, and that these windows do overlap, Window 
0 is having highest priority, Window 1 medium, and Obj Window lowest priority. 
Outside of Window is having zero priority, it is used for all dots which are not 
inside of any window region.<BR><BR><BR>
<TABLE width="100%">
  <TBODY>
  <TR bgColor=#cccccc>
    <TD><A name=lcdiomosaicfunction></A><FONT size=+2>&nbsp;LCD I/O Mosaic 
      Function</FONT></TD></TR></TBODY></TABLE><BR><B>400004Ch - MOSAIC - Mosaic Size 
(W)</B><BR>The Mosaic function can be separately enabled/disabled for BG0-BG3 by 
BG0CNT-BG3CNT Registers, as well as for each OBJ0-127 by OBJ attributes in OAM 
memory. Also, setting all of the bits below to zero effectively disables the 
mosaic function.<BR>
<TABLE>
  <TBODY>
  <TR>
    <TD><PRE>  Bit   Expl.
  0-3   BG Mosaic H-Size  (minus 1)
  4-7   BG Mosaic V-Size  (minus 1)
  8-11  OBJ Mosaic H-Size (minus 1)
  12-15 OBJ Mosaic V-Size (minus 1)
</PRE></TD></TR></TBODY></TABLE>Example: When setting H-Size to 5, then pixels 
0-5 of each display row are colorized as pixel 0, pixels 6-11 as pixel 6, pixels 
12-17 as pixel 12, and so on.<BR><BR>Normally, a 'mosaic-pixel' is colorized by 
the color of the upperleft covered pixel. In many cases it might be more 
desireful to use the color of the pixel in the center of the covered area - this 
effect may be gained by scrolling the background (or by adjusting the OBJ 
position, as far as upper/left rows/columns of OBJ are transparent).<BR><BR><BR>
<TABLE width="100%">
  <TBODY>
  <TR bgColor=#cccccc>
    <TD><A name=lcdiocolorspecialeffects></A><FONT size=+2>&nbsp;LCD I/O Color 
      Special Effects</FONT></TD></TR></TBODY></TABLE><BR>Two types of Special Effects 
are supported: Alpha Blending (Semi-Transparency) allows to combine colors of 
two selected surfaces. Brightness Increase/Decrease adjust the brightness of the 
selected surface.<BR><BR><B>4000050h - BLDCNT - Color Special Effects Selection 
(R/W)</B><BR>
<TABLE>
  <TBODY>
  <TR>
    <TD><PRE>  Bit   Expl.
  0     BG0 1st Target Pixel (Background 0)
  1     BG1 1st Target Pixel (Background 1)
  2     BG2 1st Target Pixel (Background 2)
  3     BG3 1st Target Pixel (Background 3)
  4     OBJ 1st Target Pixel (Top-most OBJ pixel)
  5     BD  1st Target Pixel (Backdrop)
  6-7   Color Special Effect (0-3, see below)
         0 = None                (Special effects disabled)
         1 = Alpha Blending      (1st+2nd Target mixed)
         2 = Brightness Increase (1st Target becomes whiter)
         3 = Brightness Decrease (1st Target becomes blacker)
  8     BG0 2nd Target Pixel (Background 0)
  9     BG1 2nd Target Pixel (Background 1)
  10    BG2 2nd Target Pixel (Background 2)
  11    BG3 2nd Target Pixel (Background 3)
  12    OBJ 2nd Target Pixel (Top-most OBJ pixel)
  13    BD  2nd Target Pixel (Backdrop)
  14-15 Not used
</PRE></TD></TR></TBODY></TABLE>Selects the 1st Target layer(s) for special 
effects. For Alpha Blending/Semi-Transparency, it does also select the 2nd 
Target layer(s), which should have next lower display priority as the 1st 
Target.<BR>However, any combinations are possible, including that all layers may 
be selected as both 1st+2nd target, in that case the top-most pixel will be used 
as 1st target, and the next lower pixel as 2nd target.<BR><BR><B>4000052h - 
BLDALPHA - Alpha Blending Coefficients (W)</B><BR>Used for Color Special Effects 
Mode 1, and for Semi-Transparent OBJs.<BR>
<TABLE>
  <TBODY>
  <TR>
    <TD><PRE>  Bit   Expl.
  0-4   EVA Coefficient (1st Target) (0..16 = 0/16..16/16, 17..31=16/16)
  5-7   Not used
  8-12  EVB Coefficient (2nd Target) (0..16 = 0/16..16/16, 17..31=16/16)
  13-15 Not used
</PRE></TD></TR></TBODY></TABLE>For this effect, the top-most non-transparent 
pixel must be selected as 1st Target, and the next-lower non-transparent pixel 
must be selected as 2nd Target, if so - and only if so, then color intensities 
of 1st and 2nd Target are mixed together by using the parameters in BLDALPHA 
register, for each pixel each R, G, B intensities are calculated separately:<BR>
<TABLE>
  <TBODY>
  <TR>
    <TD><PRE>  I = MIN ( 31, I1st*EVA + I2nd*EVB )
</PRE></TD></TR></TBODY></TABLE>Otherwise - for example, if only one target 
exists, or if a non-transparent non-2nd-target pixel is moved between the two 
targets, or if 2nd target has higher display priority than 1st target - then 
only the top-most pixel is displayed (at normal intensity, regardless of 
BLDALPHA).<BR><BR><B>4000054h - BLDY - Brightness (Fade-In/Out) Coefficient 
(W)</B><BR>Used for Color Special Effects Modes 2 and 3.<BR>
<TABLE>
  <TBODY>
  <TR>
    <TD><PRE>  Bit   Expl.
  0-4   EVY Coefficient (Brightness) (0..16 = 0/16..16/16, 17..31=16/16)