How to set up video mode?

[Synthpopalooza]

The other mode of curious interest is ANTIC 6/7 ... better known as Graphics 1 and 2

 

The character grid is laid out in bitpairs like in ANTIC 4/5 (4x8 char, 4 colors per cell)

 

screen codes 0-31 are undisplayable.

 

For Graphics 9 and 11, here are the layouts

 

screen codes: 00 01 10 11

32-63 0 1 4 5

64-95 0 2 6 8

96-127 0 3 10 13

 

For Graphics 10:

 

screen codes 00 01 10 11

32-63 PM0 PM1 BAK PF1

64-95 PM0 PM2 BAK BAK

96-127 PM0 PM3 BAK PF3

 

There is no PF0 or PF2 in this mode, and the second range only allows 3 colors. This is a mode that I have used in demos using a Super IRG style mode for Graphics 1.

[kenjennings]

I C.

What about a (structured) list about difference between A8 and C64? I am pretty sure the C64 people on AA will help.

It could be a post in this thread to which AA users can point the next "convert"

Of course along with a link to the "Altirra HW-Manual" to explore the details.

 

The Wikipedia pages have these lists of features for ANTIC, and CTIA/GTIA. Offhand, I don't see anything missing in terms of inherent capability of the hardware.

 

ANTIC:

• 14 different Playfield graphics modes:
  

• 6 character modes
  
  • 4 types of font/glyph rendering
    

  [*]8 map modes

• Output a variable number of blank scan lines
  
• Playfield Text and Map modes can be mixed onscreen
  
• Variable screen height up to vertical overscan
  
• Variable screen width up to horizontal overscan
  
• Vertical coarse scrolling
  
• Vertical fine scrolling
  
• Horizontal coarse scrolling
  
• Horizontal fine scrolling
  
• Soft, re-definable character set.
  
• Performs the DMA for CTIA/GTIA to produce Player/Missile graphics
  
• Trigger a CPU-serviced interrupt routine at specific scan lines
  
• Non-fixed RAM. This allows RAM for graphics features to be located almost anywhere in the 16-bit memory address range. This applies to:
  
  • Display lists.
    
  • Playfield Graphics data
    
  • Character set fonts
    
  • Player/Missile Graphics data
    

CTIA and GTIA:

• It is responsible for interpreting the Playfield graphics data stream from ANTIC to apply color to the display.
  
• The GTIA version includes three alternate color interpretation modes for the Playfield graphics.
  
  • 16 shades of a single hue from the 16 possible hues in the Atari palette. This is accessible in Atari BASIC as Graphics 9.
    
  • 16 hues in a single shade/luminance value. This is accessible in Atari BASIC as Graphics 11.
    
  • 9 colors per horizontal line in any hue and luminance from the entire Atari palette of 128 colors accomplished using all five playfield color registers, and the four player/missile color registers. This is accessible in Atari BASIC as Graphics 10.
    

  [*]It merges four Player and four Missile overlay objects (aka sprites) per scanline with the Playfield graphics.

  [*]It checks for collisions between the Players, Missiles, and the Playfield graphics.

  [*]It is responsible for reading the state of the joysticks' triggers (bottom buttons only in case of Atari 5200 controllers).

  [*]It contains four input/output pins that are used in different ways depending on the system:

  • In Atari 8-bit computers, three of the pins are used to read state of the console keys (Start/Select/Option).
    
  • The fourth pin controls the speaker built into the Atari 400/800, used to generate keyboard clicks. On later models there is no internal speaker, but the keyclick is still generated by GTIA and mixed with the regular audio output.
    
  • In the Atari 5200, the pins are used as part of the process that reads the state of the joysticks' keyboards.
    

[Sdw]

BTW, I would love to see your dither-plasma!

 

Here it is, finally released!

And on

as well.

[Rybags]

Nicely done. So this is Mode 4 using just 3 foreground colours?

[Sdw]

Nicely done. So this is Mode 4 using just 3 foreground colours?

 

Indeed it is, so very straightforward. But you got to start somewhere!