Posted By
MikeZ
on 2010-08-22
09:46:11
 |  Re: Voltage conversion from UK to US
gerliczer,
Yes, of course you are correct about generation of the system clock signal.
I was concerned about exactly how "jiffies" are created. The Kernal updates the jiffy clock during each raster interrupt at raster line $CC. That is a definition of a juffy. But, that only works when interrupts are enabled. The NTSC freq of 894khz divides exactly into a factor of 60 and the PAL freq of 884Khz divides exactly into a factor of 50. So, it is easy to see that a jiffy could be derived from the basic oscillator frequencies. Yet, the "jiffy" clock depends on raster interrupts instead of a strict hardware timer countdown to create a jiffy. I suppose that if you derived the time it takes for one raster vertical count cycle (From $CC to the next$CC) you would also come up with the value of 1/60th or 1/50th of a second??
Any thoughts??
Anyway, I thought I had read somewhere that the concept of a "jiffy" was tied to the powerline freq and I stand corrected with regard to the issue here.
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