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Measuring time on CPC more precisely
Posted: Sun Nov 19, 2023 1:05 pm
by ldir_hector
With ugBasic you can measure time with TIMER instruction, that gives the the time spend since your computer boot up. The time unit is 1/50 second which is quite precise, but the Amstrad CPC is able to do better !
Thanks to the following code :
Code: Select all
BITMAP ENABLE(320,200,4)
CLS
DECLARE SYSTEM PROC scnkey AT $BB06 ON CPC
DECLARE SYSTEM PROC myTime AT $BD0D ON CPC
DIM de AS WORD
DIM hl AS WORD
PRINT "Attendez un peu, et appuyez sur une touche "
CALL scnkey
ON CPUZ80 BEGIN ASM
CALL $BD0D
LD (_de),DE
LD (_hl),HL
END ASM
DIM time AS FLOAT
time = (de*256.0 + hl)/300.0
PRINT time ; "secondes"
Now you can measure time 6 times more precisely !
Re: Measuring time on CPC more precisely
Posted: Mon Nov 20, 2023 6:33 pm
by spotlessmind1975
Hi
ldir_hector, wow, that's a very creative way to leverage ugBASIC and measure time!
ldir_hector wrote: ↑Sun Nov 19, 2023 1:05 pm
The time unit is 1/50 second which is quite precise, but the Amstrad CPC is able to do better !
It almost makes me want to add a "raw" timer, i.e. the possibility of actually reading the real timer of the hardware instead of the PAL/NTSC normalized one. I don't know whether to call it
REAL TIMER or
RAW TIMER, what do you think?
Ok, I see that this system call fetches a full 32 bits, and there is no way to declare a system procedure that can pass this value through more than one register, and return a value of 32 bits on more than one register.
It's time to add it. 
Re: Measuring time on CPC more precisely
Posted: Tue Nov 21, 2023 8:57 pm
by ldir_hector
I think that REAL TIMER is confusing, as many would consider that there is a real time clock with the hour stored when the computer stops.
So Raw Timer is better, but I don't know if there is a more precise timer on every computer you support ?
Even worse, from what I understood, the Oric Atmos has no way to synchronize with the VSync ! There is an electronic soldering to do, to be able to do so but it's not standard !