Subject: Re: [stella] New jumptable implementation. From: Thomas Jentzsch <tjentzsch@xxxxxx> Date: Fri, 3 Jan 2003 11:26:51 +0100 |
Rob Mundschau wrote:: > This is my first post, so let me start by introducing myself. My name is > Rob Mundschau. I never programmed for the 2600 before, but I do have > considerable experience programming the Commodore 64. Lately I have grown > interested in the 2600 Homebrew scene, and I hope to make some games. Welcome Rob! > I have been browsing the archives, and I haven't found any mention of > technique I know of for implementing a jump table. Excuse me is this was > mentioned before, and I missed it. The smallest implementation I saw on the > list so far is: > snip > Using the PHA instructions saves 2 bytes of ROM. The RTS takes one more > clock cycle than the indirect JMP instruction so the routine takes one clock > more overall. The little advantage of the JMP() version is, that it doesn't need extra stack RAM. Instead you can re(!)use two other currently unused bytes (e.g. a pointer). And too little RAM is always a problem. :-) Have?fun! Thomas _______________________________________________________ Thomas?Jentzsch?????????|?***?Every?bit?is?sacred?!?*** tjentzsch?at?web?dot?de?| ______________________________________________________________________________ PREMIERE: Der Countdown laeuft! 3 Monate gratis + d-box 1 ab 1 Euro nur noch wenige Tage zu haben! http://premiere.web.de/?mc=999927&lp=2 ---------------------------------------------------------------------------------------------- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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