# Raster paper

This is a simple but very useful tool for C64 demo coding. It's a grid, 63 squares wide, that you print out on paper and draw instructions on. Along the top are helpful reminders about which clock cycles are involved in various effects, and which ones get stolen due to badlines and sprite fetches.

I have found this to be immensely helpful when developing effects that combine several VIC tricks.

Print a couple of copies and bring them with you on long trips. Don't forget pencil and eraser!

Posted Saturday 30-Mar-2013 18:23

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Anonymous
Sun 31-Mar-2013 05:04
I'd love to see a scanned version of your use of this paper, Linus =)
Anonymous
Tue 2-Apr-2013 00:20
I didn't understand how it can help you? can you show me a little example
how it works for you?
Anonymous
Tue 2-Apr-2013 03:22
I'd love to see a scanned version of your use of this paper, Linus =)
Anonymous
Wed 10-Sep-2014 20:07
This is extremely helpful in timing your code! Have saved hours of debugging. Thanks!
Anonymous
Wed 18-Mar-2020 00:29
I too would like to see examples. I look at this and once again, it seems to be a little short on details that those of us who are just learning would need.
quiss
Matthias Kramm
Thu 21-Apr-2022 19:28
What's "repeat last"?
Anonymous
Sat 23-Apr-2022 15:02

quiss wrote:

What's "repeat last"?

On the last line of a character row, where RC = 7, you can trick the VIC chip into keeping RC at 7. In the first half of cycle 58, if RC is 7, VIC goes into idle mode. Then, under normal circumstances, the following line is a badline (which will set RC to 0 on cycle 14, among other things). But we can write YPOS (in d011) to trigger a badline after the first half of cycle 58. Then, on the following line (which is now *not* a badline), VIC is in display mode but RC remains 7.

In char mode, this will repeat the last line of the currently loaded characters, and the trick can be repeated for every rasterline. By switching font and VIC banks, this can be used for FPP effects without wasting cycles on new fetches, but the downside compared to regular FPP is that you only have a limited number of banks available.
Anonymous
Sat 23-Apr-2022 15:08
I'll add that this is essentially a way to do linecrunch by triggering a badline very late on a rasterline, instead of removing the badline condition very early on the following rasterline. Either method may be preferable in a given situation, e.g. due to sprite DMA timing.