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dosin



Joined: 24 Aug 2007
Posts: 337
dosin
I am looking for info on programming a disk Timer or a timer in general..
info on iqr6..
no-bios
It would be for PMode

I been looking can't find much...

example:
start timer
stop timer
ect...

Thanks in advance!
Post 28 Nov 2007, 03:12
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rhyno_dagreat



Joined: 31 Jul 2006
Posts: 487
Location: Maryland, Unol Daleithiau
rhyno_dagreat
Image

Laughing

Jokes aside, though, go here:
http://www.osdever.net/bkerndev/index.php

and check the tutorial on the PIT.

It's pretty handy.
Post 28 Nov 2007, 03:24
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dosin



Joined: 24 Aug 2007
Posts: 337
dosin
lol! thanks!
Post 28 Nov 2007, 03:30
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rhyno_dagreat



Joined: 31 Jul 2006
Posts: 487
Location: Maryland, Unol Daleithiau
rhyno_dagreat
No problem! Very Happy Though I forgot that the timer IRQ went off every 18.222 seconds, though I knew it was constantly on (even from the start) because when I had it activated in my OS it would constantly display a message and not give room for anything else to operate. I have to re-write it before I enable it again. XD
Post 28 Nov 2007, 03:32
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LocoDelAssembly
Your code has a bug


Joined: 06 May 2005
Posts: 4633
Location: Argentina
LocoDelAssembly
Quote:

hough I forgot that the timer IRQ went off every 18.222 seconds, though I knew it was constantly on (even from the start)

Maybe I'm misreading you but, wouldn't it be 18.222 interrupts per second rather than the timer turns off every 18.222 seconds?
Post 28 Nov 2007, 03:55
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bitRAKE



Joined: 21 Jul 2003
Posts: 2915
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bitRAKE
IIRC, there is a way to acknowledge the IRQ has been handled - resetting the delay counter. Otherwise, it fires off every chance it gets.
Post 28 Nov 2007, 04:22
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rhyno_dagreat



Joined: 31 Jul 2006
Posts: 487
Location: Maryland, Unol Daleithiau
rhyno_dagreat
LocoDelAssembly wrote:
Quote:

hough I forgot that the timer IRQ went off every 18.222 seconds, though I knew it was constantly on (even from the start)

Maybe I'm misreading you but, wouldn't it be 18.222 interrupts per second rather than the timer turns off every 18.222 seconds?


You're right. I apologize, though what you said is actually what I meant to type. Laughing
Post 28 Nov 2007, 05:02
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sinsi



Joined: 10 Aug 2007
Posts: 693
Location: Adelaide
sinsi
Try this file - I can't remember where I got it from, but it's pretty good.

Although I would use 1193 instead of 1192 - this gives 1000.15 vs 1000.99


Description:
Download
Filename: fast_tmr.asm
Filesize: 3.46 KB
Downloaded: 105 Time(s)

Post 28 Nov 2007, 05:20
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edfed



Joined: 20 Feb 2006
Posts: 4237
Location: 2018
edfed
1000 int/second is too much
int spend time
push eflag, push eip, push cs
pop cs, pop eip, pop eflag

these 6 inherent instructions are repeat 1000 time/second.
it's too much

for my OS, i'm thinking about a 110Hz timer; cnt=10847,1
closer to 110 int/second, musical frequency 'LA'
or 24int/second for cinema FPS, cnt=49715,19{6}

or a real integral int/second, to see later.


PS: one strange thing, 1193182Hz is 1234DEh, note the 1234 string
amazing, no?
Post 28 Nov 2007, 05:55
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sinsi



Joined: 10 Aug 2007
Posts: 693
Location: Adelaide
sinsi
That's the beauty of the code - just change "mov ax,1192" to your chosen divisor and you can go from 18.2 to 1,193,182(theoretically), but the comments say that a pentium 100(?) can run at 100,000 ticks/sec.

push,push,push/pop,pop,pop - this takes no time now (or at least very little) - it's all automatic.
Post 28 Nov 2007, 06:07
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roboman



Joined: 03 Dec 2006
Posts: 122
Location: USA
roboman
http://www.powerbasic.com/files/pub/asm/8259.ZIP
is a good doc on the int chip on the pc. Also if you dig around in a lot of stepper motor control programs they use either the 8259 timer or the pent cpu built in timer
Post 28 Nov 2007, 07:20
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dosin



Joined: 24 Aug 2007
Posts: 337
dosin
Thanks- I'll take a look!
Post 28 Nov 2007, 08:00
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edfed



Joined: 20 Feb 2006
Posts: 4237
Location: 2018
edfed
in case of cached stack, it is really fast. but takes at least 6 PUSH/POP, 6 cpu cycles.
but if the stack is in real ram, then you must wait RAM latency, it's a long time. more than 6 cpu cycle
ok , it's only 6 Push/pop, but in am, we shall code the fatest program as possible.
what about the 44100Hz audio sample rate? how to make this one stable?
is it integrated in the sound chip or the DMA controler?
Post 28 Nov 2007, 14:00
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Dex4u



Joined: 08 Feb 2005
Posts: 1601
Location: web
Dex4u
If in your clocktick IRQ it increaser's a counter every tick, from startup of your OS.
You just need function that gets count.
Example
Code:
mov ax,6 ;function numberint  40h  ; int 40 like dos in 21hmov dword[StartCount],ebx  ;returns tick so far in EBX;do what you want timed heremov ax,6 ;function numberint  40h  ; int 40 like dos in 21hsub ebx, dword[StartCount]  ;sub the start ticksmov dword[StopTime],ebx  ; save the ticks that have passed.    
Post 28 Nov 2007, 17:44
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edfed



Joined: 20 Feb 2006
Posts: 4237
Location: 2018
edfed
value for the nearest integral value of 100

1193182 / 14551 = 82Hz

good because integral, no decimal...
Post 14 Dec 2007, 04:03
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17279
Location: In your JS exploiting you and your system
revolution
edfed wrote:
value for the nearest integral value of 100

1193182 / 14551 = 82Hz

good because integral, no decimal...
That is only an illusion. The oscillator frequencies are only approximate. You should use something similar to Bresenham's algorithm to get closest to your desired frequency.
Post 14 Dec 2007, 04:51
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edfed



Joined: 20 Feb 2006
Posts: 4237
Location: 2018
edfed
erf Laughing
by googling besenham, just now, i discover that MY line algorithm is the besenham one... Sad
i didn't know that, it's not the besenham algorithm but the edfed one... Smile
i reinvent the weel everydays, and finally, i see that my weel is circular like all others Wink

what you speak about is not the besenham algorythm, it's a digital PLL, something that regulate the frequency... Idea
Post 14 Dec 2007, 05:21
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17279
Location: In your JS exploiting you and your system
revolution
edfed wrote:
what you speak about is not the besenham algorythm, it's a digital PLL
I meant what I said, Bresenham's algorithm. It is all a matter of perspective. I treat each interrupt as an x-increment and advance the timer whenever there is a y-increment needed. It gives maximal timing accuracy on a long term average and can be no more than off-by-one in the short term. It requires no floats or decimals, it is an all integer solution and is simple to program and understand.
Post 14 Dec 2007, 06:46
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edfed



Joined: 20 Feb 2006
Posts: 4237
Location: 2018
edfed
hum, by using this in timer, one very bad thing is the quantification error, because the time of periods is variable.


Description:
Filesize: 126.44 KB
Viewed: 2560 Time(s)

time.jpg


Post 15 Dec 2007, 05:46
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 17279
Location: In your JS exploiting you and your system
revolution
edfed: You show an extreme case where the two frequencies are very close. Of course the difference will create what you see, it is called clock jitter. I already mentioned it will be 1 unit of difference maximum. So expect some severe jitter if the two frequencies are similar.

In any normal application, good programmers would to chose an interrupt frequency at least 10 times, and preferably >=20 times, the desired output frequency. That way the jitter is small enough to become imperceptible. Using ~1ms interrupt with 25 or 30 fps is a very good solution.
Post 15 Dec 2007, 06:54
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