Subject: Re: [stella] Does this look right? (clock) From: Piero Cavina <p.cavina@xxxxxxxxxxxxx> Date: Fri, 3 Oct 1997 14:01:25 +0100 |
At 16:41 +0000 2-10-1997, Erik Mooney wrote: >>>Try this. Frames, seconds, minutes, and hours count down instead of up. >>>You can deal with this later. Days count up. >> >>A problem with this clock is that it counts seconds, minutes and hours in >>hex and this means a conversion to BCD in case you want to display it. > >So simply store the numbers in BCD and use the 6502's BCD-math flag to >process them. I did this for the scores in my invaders game. It takes one >byte per field (frames, seconds, minutes, hours, days) in either hex or >BCD. > >Simply put a SED at the beginning and a CLD at the end of the routine I >posted, and change the #60 to #$60 and #24 to #$24. hmmm.... >>If you can modify it so it counts DOWN to 0 for each value, it becomes much >>more simpler again. >> >>dec FRAMES >>bne DoneClock >>lda #60 >>sta FRAMES >>dec SECONDS >>bne DoneClock >>sta SECONDS ;A was already 60 so no need to reload it >>dec MINUTES So you say that DECs would work in BCD afer a SED? You may be right, but I admit I have never checked this. P. -- Archives updated once/day at http://www.biglist.com/lists/stella/archives/ Unsubscribing and other info at http://www.biglist.com/lists/stella/stella.html
Current Thread |
---|
|
<- Previous | Index | Next -> |
---|---|---|
Re: [stella] Does this look right? , Erik Mooney | Thread | Re: [stella] Does this look right? , Erik Mooney |
Re: [stella] More Clock Woes, crackers | Date | Re: [stella] Does this look right? , Erik Mooney |
Month |