Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!qucdn!leek
From: LEEK@QUCDN.QueensU.CA
Newsgroups: comp.sys.amiga.tech
Subject: Re: Phi-2 Frequency on the CIA-B Chip
Message-ID: <90099.133437LEEK@QUCDN.BITNET>
Date: 9 Apr 90 17:34:37 GMT
References: <10713@netcom.UUCP>
Organization: Queen's University at Kingston
Lines: 20


In article <10713@netcom.UUCP>, mcmahan@netcom.UUCP (Dave Mc Mahan) says:
>
>I have written a short test program that measures the frequency of the Phi-2
>clock signal on the CIA-B chip.  With repeated measurements over varying
>periods of time, I keep finding the clock frequency is about 713 KHz.  Is this
>correct?  I would have guessed that it is either the system clock (7.14 MHz)
>or the colorburst frequency.  Are my math calculations wrong?  If it IS
>713 KHz, where is this generated from?
>
>  -dave

The Phi-2 (or 02) clock is generated by the E clock circuit on board the 68000.
It is 1/10 of the frequency at the clock input pin of the 68000.  It allows
the 68000 to use the older 6800 series perpherial chip.    In this case
Phi-2 = 7.16 MHz/10 = 716 KHz.  So your calculation is very good !!!

K. C. Lee

No disclaimers because no ideas were expressed... :)