Re: Procep SECAM Re: C16/Plus4

From: Gerrit Heitsch <>
Date: Wed, 02 Nov 2011 18:49:34 +0100
Message-ID: <>
On 11/02/2011 02:12 PM, Richard Atkinson wrote:

> (Incidentally as yet another aside, I wonder how the
> 6560/6561 VIC-I chrominance encoding works, as it predates this patent, and
> in the case of the 6561 it only receives PAL subcarrier frequencies at 1x
> subcarrier frequency)

You sure about that? According to

the PAL VIC in the VC-20 uses a Crystal at twice PAL clock and the chip 
has 2 clock inputs, one of them is the clock after being run through a 
74LS74. Makes me wonder if they did some dirty tricks with this.

The NTSC-VIC uses the normal 14.318MHz crystal (according to the schematic).

Also, even though the 6560 is older than the patent, as far as I know 
they did backport some of the things they learned when designing the ill 
fated 6562 to the 6560/61.


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Received on 2011-11-02 18:00:21

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