Welcome to probably the only

		 _______       ________      _______
		//      \     |	      	    //      \
	       //	 \    |		   //        \
	      //	  \   |	     _    //          \
	    _//------------\_ |_______| _//------------\_

	Docfile in exsistance.


  This docfile has been split up into different sections :-

	A - Screens
	B - Colour Palette Setup
	C - Hardware Sprite
	D - Quater Pixel Scrolling

  Although after reading through this file and studying the included
 source code you will be able to program the  AGA  chipset there are
 probably a fews things missing, but its nothing I needed to know.



Section  (A)    Screens
~~~~~~~~~~~~~~~~~~~~~~~
  The new chipset enables you to have eight bitplanes instead of the
 old six which gives you screens with upto 256 colours or 262,144 in
 HAM8. Another bonus  of eight  bitplane is  that the Dual Playfield
 mode now can have two 16 colour screens instead of 8.

 Enabling the screen modes :-

      Setting the register $dff100 (Bplcon0) to the following values
 will give you the enhance screens.

	$7200	-   Selects 7 bitplanes

	$0210	-   Selects 8 bitplanes

	$0a10	-   Selects 8 bitplanes with HAM8

  Also the register $dff1fc (Fmode) must be set to $0003.


 Modulos
 ~~~~~~~
  The modulo values for an eight bitplane interleaved screen are what
 you would  expect 40*7, but for some  reason ( and this goes for all
 number of planes) 8 has to be  taken off to give you 40*7-8. This is
 the same for both bpl1mod and bpl2mod.


Section  (B)    Colours
~~~~~~~~~~~~~~~~~~~~~~~

  In the old chipset a colour value ranged from 0-4096 giving you a 12
 bit colour value ie. $fff is white. Now the new  chipset can select a
 colour from 16,777,216 which means the  colour value is 24 bit.

  One problem we have is that the amiga has  only 32 colour  registers
 and we sometimes need to set upto 256  different colours, so does the
 new chipset have 256 colour registers ? NO. What the chips do is they
 split the 256 colours up, firstly they are separated into eight banks
 of 32 colours then split again into two  word values ie. colour value
 $fefefe which is almost 24 bit  white is split to give $fff and $eee.
 What you have now is two sets of 8 * 32 colour  banks one for the top
 4 bits of each RGB component and one for the bottom 4 bits.

  To select a bank of 32 colours to set we use $dff106 (bplcon3) this
 when set to a certain value will enable you to change a certain bank
 of colours or bits. The top 4 bits of your  colour  have to set this
 register to one of  eight values ( $0c40, $2c40, $4c40, $6c40, $8c40
 $ac40, $cc40 and finally $ec40). The  bottom 4 bits are accessed the
 same way except the $c40 is changed to $e40.


Section  (C)    Sprites
~~~~~~~~~~~~~~~~~~~~~~~

  One of the  enhancements  which was long overdue was bigger sprite,
 these can now be upto 64 pixels wide ( but still only 8 and the same
 colour selection applies ie 4 or 16 colour attached).

  To enable the extra wide sprites the  register $dff1fc (Fmode) must
 be set to $000c, then the other thing to notice is that the  control
 words have moved slightly :-

	Old way    Control Word1  Control Word2

			    V	   V
			    |	   |
			    V	   V

   MySpriteData  dc.w      $9c3c,$cc00


	New way       Control Word1

			    V
			    |
			    V

   MySpriteData  dc.w      $9c3c,$0000,$0000,$0000
  		 dc.w      $cc00,$0000,$0000,$0000

			    ^
			    |
			    ^

		      Control Word2


Section  (C)    Scrolling
~~~~~~~~~~~~~~~~~~~~~~~~~

  The new chipsets hardware scroll feature has been  changed so that
 you can now move in quarter increments, this can give you very nice
 raster scrolls.

  The register used  is still  $dff102 (bplcon1), but extra bits are
 now used. For example :-

   To scroll all even planes we use bits 0-3 for normal scroll.

   For quarter scroll we use the above bits plus bits 8-9.

   Also there is extended scroll to move the screen more than 16 pixels
   these bits are 10-11.

  This in total gives you a scroll value from 0-255 although you only
  move 64 true pixels the rest are just quarter steps.


Extra Information
~~~~~~~~~~~~~~~~~

	All graphical information on the A1200 is fussy about the
 boundary its placed on ie word or long word. The  easiest way to
 get around this is to use a section statement before each incbin
 you use.


     All the above things mentioned have an example file included
 on this  disc for  you to mess about with, they were all written
 using Hisoft Devpac v3.04.

	Hope this helps you out and gets more A1200 only games on
	the scene.


	      / /
	     / /
	    / /
	\ \/ /
	 \/\/		Amiga Forever !!!!!