Wanted: Cycle correct Countdown Timer

[Itchy Scratchy]

Polishing up my game and I am running into small issues that some of you brains might be able to help with.

 

One, I am running out of time because of Christmas and Grand kids flopping about.

Two, I am running out of time because of Christmas and Grand kids flopping about.

 

With that I would ask if anyone in the community has an accurate count down timer like that featured in Donkey Kong, Blasto or your common core game with a count down timer.

 

I have two players competing for merchandise on the screen with a count down so the higher score wins after time out.

 

My routines work but they are iffy at best so if there is a professional formula that also shows a 3 digit display anywhere on screen

 

Please, code must be in Z80 assembly.

 

Tony Cruz gave me some insight on BCD and now I am thinking I was pretty dag on good with my coding, I have done some things you shall see, however this went over my head and just did not work the way I thought it would.

 

A simple 3 digit display timer that counts increments of 1's from 199 to 0.

 

 

TIA always.

[Kiwi]

I may not know z80.  One simple way is to 3 variables to hold a single digit.  1 variable to count to 60.  To place number on screen, like put_char(3,2,48+digit1);put_char(4,2,48+digit2);put_char(5,2,48+digit3); Whenever a digit roll hit 255, then reset digit to 9, and deduct the 2nd or/and 3rd digits.  If (digit1==0 && digit2==0 && digit3==0){TimesUp();}. 

My other 3 digit uses MOD(%) and uses 1 variable.

a=SP/10;
b=SP%10;
if(SP<100){f=0;}
if(SP>=100){f=1;a-=10;}
if(SP>=200){f=2;a-=10;}
put_char(0,17,'S');
put_char(1,17,f+48);
put_char(2,17,a+48);
put_char(3,17,b+48);

Maybe this information could help you.  Sorry it's not in Z80. The x,y (3,17 can translate to 0x1800+3+17*32)

[Itchy Scratchy]

What I can ultimately do is have a 0-9 print routine then print the ones, deduct the tens then print, deduct the hundreds then print.

It's convoluted so I thought there may be a standard someone was willing to share.

 

As far as the actual timer part, I am getting the feeling that close enough should be fine.  It's a game and not sending a man to the moon.

 

Thank you Kiwi for the input.

[Itchy Scratchy]

Thanks to everyone, I went ahead and wrote it long hand then optimized it.

Not such a big deal, just check in multiples of ten.

 

However I want to go back to my call on a thread to have the most optimized Z80 routines for the Colecovision which anyone can grab for game development or even adapt them for other systems.

 

To be honest I have no idea why this has never been done.  At least where I could find.

Along with some Z80 classes I may just go ahead and start this endeavor as a new 2021 project.

I don't want to bite off more than I can chew because I am finding out there is more I can learn like BCD.