Memory.md

Currently the Base address of the VDC is $FF00 ( this may change before release )

VDC Control.

$00 - Video Display Page.

$0-$F directs the display controller to point to $n000 in memory 

$01 - Video Display Colors.

$00-$FF directs the color ram to $nn00 in memory. 
768 bytes of color data ( subject to change ) 

Input

$02 - Controller input

Blitter Control.

$03 - Xposition

( signed int 8 ) 0 is left edge.

$04 - Yposition

( signed int 8 ) 0 is top edge 

$05 - Width

( signed int 8 ) negative values create X flipped data of abs(width) 

$06 - Height

( signed int 8 ) negative values create Y flipped data of abs(height)

$07 - Data stride

the data increment per Y scanline of data.

$08 - X Scale

2:6 bit fixed point. $40 = 1 pixel per pixel $20 is half size

$09 - Y Scale

2:6 bit fixed point. $80 = 2 pixel per output pixel 

$0A - Data page

Output ram page, $0-$F writes to $n000 page 

$0B - Source of data LOW BYTE

$0C - Source of data HI BYTE

$0D - Trigger and control.

	- write to this AFTER setting above registers. writing to this byte triggers the Blitter CHIP
	- %x------- skip colorkey value, don't write if source contains Key 
	- %_x------ use X & Y bytes as ADDRESS to write, vs X&Y screen position. ( ignores Page )
	- %--xx---- bits per pixel of source data. 
	     00     1 bit per pixel data ( Useful for fonts ) 
	     01     2 bit per pixel data 
	     10     4 bit per pixel data 
	     11     8 bit per pixel data 
	- %----xxxx color palette control, depends on BPP source data 
	       BPP1 xxxx is literal offset into palette 
	       BPP2 xxxx is xxxx * 4 e.g. 1 adds 4 to input color index, 2 adds 8 etc. 
	       BPP4 xxxx is xxxx * 16 e.g. 1 adds 16 to input color index , 2 adds 32 etc. 
	       BPP8 serves no purpose currently

$0E - Color Key value

if Trigger has %10000000 set blitter will ignore this value 

$0F - experimental bits.

- 0 draw normally 
- 1 draw transparent. 
	to be explained 

$1D-$1E - IRQ pointer - NOTE NOTE NOTE - irq pointer is not at $fffe

$1F - Device control bits

%00000000 - video acts like the original minicube.

%-------x - RGB444 16 bit ( no alpha )

%x------- - screen update per 8 cycles vs at end of frame. Dynamic palette change mid frame possible.

Audio

6 channel Namco WSG style chip.

Extended to add 3 additional channels

Extended to support 16 waveforms vs 8

Samples are encoded as 32 nibbles vs 32 bytes ( 16 bytes per sample )

Stored in per channel consecutive bytes.

$20-25 - Memory Page for Audio Channel, $nn00 source ram for audio sample

$26-2B - ControlBits 	%xxxx---- volume 
						%----xxxx waveform select
$2C-31 - Frequency low msb
$32-37 - Frequency hi msb

TODO

Clarify blitter cycle speeds.