[ Usenet FAQs | Web FAQs | Documents | RFC Index ]
Single Page
Top Document: Atari 8-Bit Computers: Frequently Asked Questions
Previous Document: 1.11) What are SALLY, ANTIC, CTIA/GTIA/FGTIA, POKEY, and FREDDIE?
Next Document: 1.13) What is the internal layout of the 8-bit Atari?
-
Search the FAQ Archives
Single Page
Top Document: Atari 8-Bit Computers: Frequently Asked Questions
Previous Document: 1.11) What are SALLY, ANTIC, CTIA/GTIA/FGTIA, POKEY, and FREDDIE?
Next Document: 1.13) What is the internal layout of the 8-bit Atari?
1.12) Why do the ANTIC Modes start with "Mode 2", what about 0 or 1?
This section started by: Laurent Delsarte
Actually, the ANTIC graphic mode numbers are directly used as instructions
in Display Lists (DL), to request the display of several lines of a specific
text or graphic mode. For instance, the instruction "2" (for "Mode 2") in an
ANTIC Display List requests 8 scan lines of "text 0".
But the instructions "0" and "1" already have other meanings in an ANTIC
Display List program:
"0" means "display one blank line"
"1" means "jump to location"
and to be comprehensive, 16 (hex: 10), also means something special:
"16" means "display two blank lines"
Consequently, the first ANTIC mode is the "Mode 2", and the last one is
"Mode 15".
Here is the context of the full ANTIC display list instruction set:
Instruction BASIC Scan Pixels Bytes Comments
Decimal Hex mode lines line line
Blank Line instructions
0 0 -- 1 -- -- 1 blank line
16 10 -- 2 -- -- 2 blank lines
32 20 -- 3 -- -- 3 blank lines
48 30 -- 4 -- -- 4 blank lines
64 40 -- 5 -- -- 5 blank lines
80 50 -- 6 -- -- 6 blank lines
96 60 -- 7 -- -- 7 blank lines
112 70 -- 8 -- -- 8 blank lines
Character Mode instructions
2 2 0 8 40 40 text mode 0
3 3 -- 10 40 40 text mode *
4 4 -- 8 40 40 text mode *
5 5 -- 16 40 40 text mode *
6 6 1 8 20 20 text mode l
7 7 2 16 20 20 text mode 2
Map Mode instructions
8 8 3 8 40 10 graphics mode 3
9 9 4 4 80 10 graphics mode 4
10 A 5 4 80 20 graphics mode 5
11 B 6 2 160 20 graphics mode 6
12 C -- 1 160 20 graphics mode *
13 D 7 2 160 40 graphics mode 7
14 E -- 1 160 40 graphics mode *
15 F 8 1 320 40 graphics mode 8
Jump instructions (three bytes long)
1 1 -- -- -- -- JMP -- jump to location
65 41 -- -- -- -- JVB -- jump and wait for
vertical blank (VBLANK)
Modes marked with an asterisk (*) have no equivalent in BASIC.
Optional Modifiers to the above Character or Map Mode instructions:
add add
decimal hex bit
Vertical scroll 16 10 4
Horizontal scroll 32 20 5
LMS Load Memory Scan 64 40 6
Optional Modifier to the above Blank Line or Jump instructions:
DLI Display List Interrupt 128 80 7
More details of ANTIC display list programming can be found in the book
"Mapping the Atari", Appendix 8
http://www.atariarchives.org/mapping/appendix8.php
and also in the book "De Re Atari", Chapters 2, 5 and 6
http://www.atariarchives.org/dere/chapt02.php ANTIC and the display list
http://www.atariarchives.org/dere/chapt05.php Display List Interrupts
http://www.atariarchives.org/dere/chapt06.php Scrolling
Top Document: Atari 8-Bit Computers: Frequently Asked Questions
Previous Document: 1.11) What are SALLY, ANTIC, CTIA/GTIA/FGTIA, POKEY, and FREDDIE?
Next Document: 1.13) What is the internal layout of the 8-bit Atari?
Single Page
[ Usenet FAQs | Web FAQs | Documents | RFC Index ]
Send corrections/additions to the FAQ Maintainer:
Michael Current <michael@mcurrent.name>
Last Update October 22 2009 @ 05:22 AM