Display is a 512x392 write only buffer.
The visible region is a window(480x360 or 240x180) into FrameBuffer

Serial Pixel Mode

Pixels can be written to the buffer one at a time through a serial interface

	0x20...0x22:
		The serial write address is a 24 bit offset into the display buffer  

	0x23:
		The Serial Pixel Control register contains flags indicating how the serial write operations behave.

The serial pixel pointer may be auto incremented on any of the serial write operations.

	bit 0x10   increment serial write address after ADD operation
	bit 0x20   increment serial write address after SUB operation
	bit 0x40   increment serial write address after MUL operation 

The value written from a serial write operation will be the value writeent to the operator port ADD,SUB or MUL combined with either the existing colour at that pixel location or a base colour holding a colour index into the 256 colour palette.

	bit 0x01  if set ADD uses the baseColour
	bit 0x02  if set SUB uses the baseColour
	bit 0x04  if set MUL uses the baseColour
				
0x24: 
	Serial Pixel Base colour.  
	Index to the coloour in the fixed 256 colour palette

To set a serial pixel to a fixed colour, using the ADD operation combined with Black in the BaseColour will result in a simple SET operation ( x+0=x )

0x25:
	Serial write ADD
	When writing 8 bit value V to the port
	The pixel at the serial write address DEST will set by
	
			DEST = DEST + Palette256[V] 

	or - if bit 0x01 is set in the Serial Pixel Control Register
	
			DEST = Palette256[BaseColour] + Palette256[V] 

	Red, Green, Blue levels are added seperately and do not pass their max value.


0x26:
	Serial write SUB
	When writing 8 bit value V to the port
	The pixel at the serial write address DEST will set by
	
			DEST = DEST - Palette256[V] 

	or - if bit 0x02 is set in the Serial Pixel Control Register
	
			DEST = Palette256[BaseColour] - Palette256[V] 

	Red, Green, Blue levels are subtracted seperately and do not pass their min value.

0x26:
	Serial write MUL
	When writing 8 bit value V to the port
	The pixel at the serial write address DEST will set by
	
			DEST = DEST * Palette256[V] 

	or - if bit 0x04 is set in the Serial Pixel Control Register
	
			DEST = Palette256[BaseColour] * Palette256[V] 

	Red, Green, Blue levels are multiplied seperately and considered to be in the range from zero to one. 

Display Control

0x28:
	Display Control
	writing 0x00 places the buffer image on screen in lowres mode
	writing 0x01 places the buffer image on screen in hires mode

0x29:
	Display Shift X
	The position of the left edge of the screen within the display buffer

0x2A:
	Display Shift Y
	The position of the top edge of the screen within the display buffer

The Blitter

The display buffer can also be written to via the blitter. The Blitter reads from RAM and translates a variety of formats to screen writes. The top left corner of the blit operation is the pixel specified by the current serial pixel address.

Blit operations utilize up to 16 colours from a colour table at 0x60...0x6f each value in the colour table is an index into the fixed 256 colour palette.

The address range 0x40...0x4f holds the blitter parameter space which can be different for different blit formats.

Writing to Blit Control at 0x2b selects the format and triggers the blit operation. Blit formats 0x01...0x04 utilize micro palettes and can render some colours with additive blending (and by extension by addive blending black, transparancy).

0x2B:
	Blitter Control, starts the blit operation
	0x01    8 pixels per byte.  2 colours
	0x02    4 pixels per byte.  4 colours
	0x03    3 pixels per byte.  16 colours with each set 
					of 3 pixels limited to one of four sets of 4 colours
	0x04    2 pixels per byte.  16 colours

	0x10    Mode 0  3x3 cell mode. 2 bytes per cell.  
					Cells have any 2 of 16 colours.

	0x11    Mode 1  8x8 cell mode. 2 bytes per cell.
					Cell images from 256 four-colour tiles. 
					NES mode.  X and Y tile Flipping availabe

For Blit formats 0x01...0x04 the Blitter parameters are the same with the only differences being the size of the output image and the number of colours available.

0x40:   ImageData_L    
0x41:   ImageData_H
	RAM location of the image data.

0x42:   Width of the blit operation in bytes 
0x43:   height of the blit operation in pixels

0x44:   Line increment.
	The distance in bytes between one line of image data and the next.         

0x45:   Palette_L
0x46:   Palette_H
	RAM location of the MicroPalette 16 four bit entries 
	totalling 8 bytes. Each MicroPalette entry is an index to 
	the 16 entry colour table at `0x60...0x6f`
	If MicroPalette entry equals its position the colour 
	is additive blended otherwise the blitter performs a 
	straight overwrite of the destination pixel.

	This means a pointer to a MicroPalette containing

			0x01,0x23,0x45,0x67,0x89,0xAB,0xCD,0xEF

	Would render all pixels with additive blending, whereas

			0x01,0x23,0x45,0x67,0xEF,0xCD,0x89,0xAB
	
	refers to the same colours in a different order, causing
	only the first 8 to be blended.

	To achieve the traditional sprite colour zero transparancy
	set the first micropalette entry to zero and the first 
	colour table entry to zero(black),  for exampe,

			0x0F,0xED,0xCB,0xA9,0x87,0x65,0x43,0x21

	would provide colour zero transparancy and the remaining 
	16 colours in the reverse order but solid.

0x4f:   Blit Flags
	bit 0x80 Blit is X flipped , right to left 
	bit 0x40 Blit is Y flipped, updide down
	bit 0x20 Blit is scaled to double width
	bit 0x10 blit is scaled to double height

	bits 0x0f reserved for expansion

Blit Mode0 is a 3x3 cell mode where each cell is represented by two bytes. Cells may use any 2 colours of 16.

The bits in the first byte define the 8 pixels in the 3x3 cell in the following order

The second byte provides two 4 bit indexes into the colour table indicating which two colours to use for the cell. Consider these to be Colour A and Colour B. A clear bit in the first byte denotes Colour A and a set bit denotes colour B. The bottom right pixel in the cell is always Colour A.

While the Bottom right corner is not bit addressable, all combinations of pixels are available in this format. Swapping the values Of Colour A and Colour B, while inverting the first byte, results in a change to the bottom right pixel without changing the appearance of the rest of the cell.

For instance for a cell in yellow (in palette entry 14) and blue(in palette entry 15) with this pattern

Would be encoded as 0x9E, 0xEF

To change the image to

The image would be encoded as 0x61, 0xFE which is a logical not of the first byte and a swap of the top and bottom 4 bits of the second byte.

Mode 0 Parameters are

0x40    ImageData_L
0x41    ImageData_H
				Address in ram of the image data.

0x42    Width of the Blit operation in Cells
0x43    Height of the Blit operation in Cells
0x44    Line increment. The distance in Cells between one line
				of image data and the next. As cells are two bytes, the
				distance in bytes is this value doubled.

Mode 1 is a 8x8 cell - index tile mode. Each cell is two bytes, a 8 bit tile index followed by an attribute byte to specify colours, xflip and yflip.

The index can be one of 256 tiles. Tile data is 8x8 two bits per pixel making them 16 bytes per entry and providing 4 colours per tile. The attribute byte can specify one of 16 MicroPalettes for each cell.

The attribute byte is encoded as

	XY..PPPP
				X (bit 0x80) flip cell X
				Y (bit 0x40) flip cell Y
				P (bits 0x0F) MicroPalette number.
				bits labeled . are unused at this time.

Mode 1 parameters are

0x40    MapData_L
0x41    MapData_H
				Address in RAM of the map cells

0x42    Blit Size 
				the top 4 bits indicate the width in cells of the Blit
				the bottom 4 bits indicate the Height in cells of the blit.
				the size from each 4 bit value is decoded as
				if v==0 then 1 else v*2;
				conseqently the only odd size provided is 1

0x43    Line increment. The distance in Cells between one line
				of image data and the next. As cells are two bytes, the
				distance in bytes is this value doubled.

0x44    PaletteData_L
0x45    PaletteData_H
				Address in RAM of the 16 MicroPalettes totaling 32 bytes

0x46    TileData_L
0x47    TileData_H
				Address in RAM of the Tile Set.  256*16 bytes (4k in total)

Audio

There are 8 independant voice chennels available each with identical abilities. The voices provide a variety of base waveforms, Pitch Bend, an Attack/Hold/Release envelope and individual noise and volume control.

All voices share the same hardware registers at 0x50...0x57 writing 0...7 to 0x2c Selects which voice the register range controls. There is a Master volume at 0x2e

The Attack/Hold/Release cycle is triggered by writing to 0x57 Thus it is possible to play a 'canned' sound effect by writing to the eight voice registers in turn and upon witing the last value the sound will play.

Voice registers are:

	0x50    Freq_L
0x51    Freq_H 
				Frequency is the Int16 value multiplied by 0.0596 Hz

0x52    Volume 
				Int8 value ranging from 0:silent  to 255:Max volume
				
0x53    Wave Shape
				Low 4 bits ....xxxx Wave Base: 
				0000 square, 1000 = Sine, 1111 = Triangle.
				intermediate values interpolate.
				square and triangle waves are scaled to have same area
				under curve as Sine preserving volume

				bits .xxx....  Wave shift: 
				000 = no shift, Applies a gamma curve in the time domain

				high bit x....... Modulate:
						if set, this voice is silent, instead the output is muultiplied with the next voice 

0x54    Pitch Bend
				low 5 Bits: bend Amplitude              
						Frequency range of the bend.  
						A value of 0 indicates no bend
						A value of 31 will oscillate frequency between 
								voice_freq - voice_freq/2
						and 
								voice_freq + voice_freq/2
				
				high 3 bits: Bend phase 000=0 100=Pi  111=2*PI/8*7,   

0x55    Bend duration
							Oscillation Frequency (((Uint8_Value+16)/(255+16))^4 ) * 128  Hz 
							A value of 0 results in a bend of 0.0016 Hz  ( 642 seconds for a full oscillation wave)
							A value of 1 results in a bend of 0.0079 Hz   (127 seconds for a full oscillation wave)
							A value of 16 results in a bend of 0.025 Hz   (40 seconds for a full oscillation wave)
							A value of 32 results in a bend of 0.126 Hz   (8 seconds  for a full oscillation wave)
							A value of 64 results in a bend of 0.97 Hz    (1 second for a full oscillation wave)
							A value of 96 results in a bend of 3.73 Hz     
							A value of 128 results in a bend of 10 Hz     
							A value of 192 results in a bend of 44 Hz     
							A value of 255 results in a bend of 128 Hz     

0x56    Noise Level and Envelope Hold Duration 

				low 4 bits: Noise level
						A value of 0 indicates no added noise
						A value of 15 indicates the wave will be all noise

				high 4 bits: HoldTime:
						Envelope Release starts at (Int4_Value / 8)² Seconds
						0000 is Immediate release
						0001 is release after 1/64th of a second
						1000 is release after 1 second
						1111 is release after 3.51625 seconds

0x57    Play, Attack and Release Envelope control

				low 4 bits for attack:
				high 4 bits for release:

				Duration for both is (Int4_Value / 8)² Seconds

				Writing to the this Register triggers the start of the
				Attack,Hold,Release Cycle.

Inputs

0x30    Buttons_1     Left Up Right Down Enter Esc Ctrl Space
0x31    Buttons_2     A W D S Shift (Mouse1 || Z) (Mouse2 || X)  (Mouse3 || BackSpace)    

0x32    mouseX measured in LowRes pixels 
0x33    mousey measured in LowRes pixels 

0x34    increments on each frame of host device.
0x35    increments once per second 

0x36    buffers a few chars. reads as zero when buffer is empty. reading the port removes the item from the buffer.