Chapter 2 of De Re Atari: ANTIC AND THE DISPLAY LIST. Retrocomputing podcast about the Atari 8-bit line of personal computers. Vol. 1 – No. 1. Antic issue Vol. 1 – No. 1. April – (PDF). Vol. 1 – No. 2. Antic issue Vol. 1 – No. 2. June – (PDF). Vol. 1 – No. 3. Antic issue Vol. 1 – No. 3.
|Published (Last):||28 June 2017|
|PDF File Size:||12.70 Mb|
|ePub File Size:||15.47 Mb|
|Price:||Free* [*Free Regsitration Required]|
It reloads the program counter with the value in the operand and waits for the television to perform a vertical blank. This will probably result in a garbled display.
Note that this means that display lists are not fully relocatable. For example, by changing the LMS during vertical blank, the programmer can alternate screen images. Next, another mode 0 line 40 more bytesahari a mode 8 line. This occurs if the Mode 8 or 9 line is horizontally scrolled or not, but the corruption results are different in each case.
This is done by writing machine language routines to change the values of hardware registers at different vertical positions on the screen. Go to the sample graph. The data processed by this Display List “program” is the screen memory.
Scrolling farther than the ANTIC Mode’s number of scan lines results in lines of repeated data upsetting the fine scrolling continuity though, this can also be used as an exploitable behavior. This means if something on the screen is in a given atrai mode, everything next to it is also in that same mode. We will then start examining and modifying display lists to get some nice effects. This means we can mix modes on the screen by stacking the different display blocks that we want.
It will, and the display will pop up on the TV. Two such prototype circuits were being developed, but neither entered production.
De Re Atari – Chapter 2
It may sometimes be necessary to use a second LMS instruction. In other words, the memory for the previous Mode line ends at the exact last byte of the 4K block and the next Mode line begins at the exact first byte of the next 4K block. ANTIC’s program counter has only 10 bits of counter and six bits of latch and so the display list cannot cross a 1K boundary. Modifier bit value 1 Enables the modifier, and 0 disables the modifier.
Graphics ztari 15 graphics mode Number of colors: This is because graphics 8 display blocks are atqri one scan line high.
This gives a horizontal resolution of pixels. Thus, the ultimate limit for full-color horizontal resolution with a standard color television is pixels. Furthermore, they are quite simple in structure and easy to set up. A horizontal step is accomplished by natic or decrementing all the LMS addresses of the scrolling region.
Vertical Fine Scrolling for Map modes only one scan line tall is logically not practical. The display list is a collection of code bytes that specify that sequence. This is not a serious limitation, because the size of a single Display List usually varies from 32 to bytes, and virtually never exceeds bytes.
There are many books on machine atnic. There are also four special options that can sometimes be specified by setting a designated bit in the ANTIC instruction. In this way information from all over the address space taari the computer can be displayed on a single screen.
So the people who ajtic the Atari gave the some help, in the form of a very fast, dumb slave computer called the ANTIC.
Although the mode cannot change inside a display block, the blocks above and below that display block can be in different modes. The handles all the usual computer processing; executing Basic programs, writing data to disk, and so forth. ANTIC buffers the first few bytes read from screen memory that are sufficient to cover the 16 color clock range of movement. The and ANTIC share memory, and the computer is designed to keep them from trying to use the same memory at the same time. The shadow register is the recommended source for reading this information, since it will be updated during the vertical blank guaranteeing consistent and reliable results.
This page was last edited on 8 Decemberat The usual purpose is to change display-related values at a known location so transitions are visually precise or occur where they will not conflict with display activity.
Its most obvious use is for mixing text and graphics.