Hi!, On 05/14/13 13:36, Gerrit Heitsch wrote: > ... > Until we know the actual circuit we can only guess, but with 2 Crystals, > the 2 frequencies are not in sync as they are with the old PLL circuit > based on the 74LS629. This should result in a slightly unstable picture > on the monitor, especially if you use FBAS/CVBS. > ... They usually aren't in sync in such scenario, though, there's still some chance that they are. A couple of years ago, I was "forced" to use an A520 RF Modulator to connect an Amstrad CPC to a projector. (I was not sure whether the projector was to support the standard analog RGB signal I had, thus the ugly solution of hooking a pure analog RGB source to an RGB projector using composite video). After receiving absolutely no composite color first, I was very surprised to learn that the MC1377 in the A520 had a slightly hacky color subcarrier oscillator circuit, which relied on the presence of a master clock signal which is provided by the Amiga. This master clock (7.7xMHz) is derived from the Amiga master clock, which is (in turn) an even multiple of the dot clock of the Amiga. Thus, the resulting color subcarrier clock is in sync with the machine's dot clock, even though the color encoder has a separate color subcarrier crystal and oscillator circuit. It would be interesting to know whether the SX utilizes similar tricks in order to provide sync'd dot and color clocks. Levente Message was sent through the cbm-hackers mailing listReceived on 2013-05-14 13:00:03
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