Log inRegister an accountBrowse CSDbHelp & documentationFacts & StatisticsThe forumsAvailable RSS-feeds on CSDbSupport CSDb Commodore 64 Scene Database
  You are not logged in - nap
Cycle Jitter TestProg   [2015]

Released by :
The Obsessed Maniacs

Release Date :
28 July 2015

Type :
C64 Misc.


User rating:awaiting 8 votes (8 left)

Credits :
Code .... Copyfault of Dienstagstreff, The Obsessed Maniacs

Download :
http://csdb.dk/getinternalfile.php/140247/force_cycle.zip (downloads: 387)

Look for downloads on external sites:

Production Info
Submitted by Copyfault on 27 July 2015
Old cycle jitter test prog allowing to force a raster irq condition to occur on a selected processing cycle. The current jitter value (=delay till start of irq routine [#cycles]) is printed on the text screen.

Basically the main code consists of the loop
.loop   INC $C000,X
        BPL .loop
        BMI .loop

For different jitter values you can change the following settings (adjust Source Code accordingly):
; Meta Settings
-> Set to '1' for ensure that the first branch-instruction "BPL" is taken

-> This is the no. of bytes the test code loop will be shifted _below_ $0b00 to configure different page crossing situations for the branch instructions (formula is CODE_ADRESS = $0b00 - MEM_MISALIGN)

Reasonable values are
0: no page break
1: page_break for both branch instructions
4: page_break for BMI and BPL (if taken)
5: page_break for BMI (if taken), for BPL !if not taken!
6: page_break for BMI but not for BPL

-> Use this to set the cycle no. of the irq condition
cycle 0 is the first INC_cycle, increment this value to let the irq occur at a later cycle
For ex., COND_CYCLE=8 (-> irq occurs on 2nd bpl-cycle) gives the "worst case" jitter of '7' iff branch is taken

This test prog shows that there are eight different jitter values (0,1,...,7) possible even when no unintended opcodes are used.
Search CSDb
Prev - Random - Next
Detailed Info
· Summaries
· User Comments (1)
· Production Notes (1)
Fun Stuff
· Goofs
· Hidden Parts
· Trivia
· Discuss this release
Sponsored links
Support CSDb
Help keep CSDb running:

Funding status:

About this site:
CSDb (Commodore 64 Scene Database) is a website which goal is to gather as much information and material about the scene around the commodore 64 computer - the worlds most popular home computer throughout time. Here you can find almost anything which was ever made for the commodore 64, and more is being added every day. As this website is scene related, you can mostly find demos, music and graphics made by the people who made the scene (the sceners), but you can also find a lot of the old classic games here. Try out the search box in the top right corner, or check out the CSDb main page for the latest additions.
Home - Disclaimer
Copyright © No Name 2001-2023
Page generated in: 0.08 sec.