mirror of
https://github.com/catseye/SixtyPical.git
synced 2024-11-29 18:49:22 +00:00
80 lines
2.6 KiB
Plaintext
80 lines
2.6 KiB
Plaintext
|
Ribos
|
||
|
|
=====
|
||
|
|
|
||
|
|
This little demo is intended to be a well-commented example of how to
|
||
|
|
program a raster interrupt in 6502 assembly language on a Commodore 64.
|
||
|
|
|
||
|
|
This (r)aster (i)nterrupt changes the colour of a region of the
|
||
|
|
(bo)rder of the C64 (s)creen; thus, RIBOS. Also, it's the name of a
|
||
|
|
planet from Dr. Who, if that means anything.
|
||
|
|
|
||
|
|
|
||
|
|
How to Run the Demo (using the VICE C64 emulator, x64)
|
||
|
|
------------------------------------------------------
|
||
|
|
|
||
|
|
0. Obtain VICE from http://www.viceteam.org/, install it,
|
||
|
|
and run x64
|
||
|
|
|
||
|
|
1. Mount this project's directory as drive 8:
|
||
|
|
|
||
|
|
Make sure
|
||
|
|
Peripheral settings > Device #8 > Enable IEC Device
|
||
|
|
is checked, then select
|
||
|
|
Peripheral settings > Device #8 > File system directory...
|
||
|
|
and enter the path to the project directory.
|
||
|
|
|
||
|
|
2. LOAD "RIBOS.PRG",8,1
|
||
|
|
|
||
|
|
3. SYS 49152
|
||
|
|
|
||
|
|
4. You should see the colour of the middle of the border change
|
||
|
|
while you get a READY. prompt and can continue working.
|
||
|
|
|
||
|
|
|
||
|
|
How to Assemble the Program (using the p65 assembler)
|
||
|
|
-----------------------------------------------------
|
||
|
|
|
||
|
|
0. Obtain p65 from http://hkn.berkeley.edu/~mcmartin/P65/
|
||
|
|
(I used p65-Perl version 1.1) and install it somewhere
|
||
|
|
on your path. If your Perl interpreter isn't located at
|
||
|
|
/usr/bin/perl, change the first line of p65 appropriately.
|
||
|
|
|
||
|
|
1. p65 -v -t -b ribos.p65 ribos.prg
|
||
|
|
|
||
|
|
The switches aren't necessary, but they make it feel like
|
||
|
|
p65 is doing something difficult and important. It also
|
||
|
|
isn't necessary to add the '.prg' extension on the end of
|
||
|
|
the binary object's filename, since it will appear as a
|
||
|
|
PRG file to VICE anyway, but it's nice as a reminder when
|
||
|
|
you're working in a modern operating system.
|
||
|
|
|
||
|
|
2. Follow the steps under 'How to Run this Demo' to see that
|
||
|
|
it worked.
|
||
|
|
|
||
|
|
|
||
|
|
How it Works
|
||
|
|
------------
|
||
|
|
|
||
|
|
Read the source! I've tried to make it very well-commented,
|
||
|
|
including what happens when you leave out some steps.
|
||
|
|
|
||
|
|
I wrote this demo because it was a long time since I had done any C64
|
||
|
|
programming, and, having just obtained a copy of the 'Commodore 64
|
||
|
|
Programmer's Reference Guide,' I wanted to code something challenging,
|
||
|
|
yet not too involved. I remembered raster interrupts as one of those
|
||
|
|
quintessential C64 low-level graphics tricks, so I decided to try my
|
||
|
|
hand at that. Looking around on the Internet, I found this page:
|
||
|
|
|
||
|
|
http://everything2.com/index.pl?node_id=79254
|
||
|
|
|
||
|
|
Although it's a fairly detailed description, it took me a couple of
|
||
|
|
frustrating hours to implement it successfully - both the everything2
|
||
|
|
article and the Reference Guide were pretty muddy on a couple of
|
||
|
|
points. What I learned in the process is written into the comments.
|
||
|
|
|
||
|
|
Happy raster-interrupting!
|
||
|
|
|
||
|
|
-Chris Pressey
|
||
|
|
April 10, 2007
|
||
|
|
Vancouver, BC
|