Re: C128 VDC video questions

From: Ojala Pasi 'Albert' (
Date: 2000-03-10 15:41:42

> A few questions on the output of the RGBI port on the 128...
> 1) This is TTL RGB, right?  That would make the signalling levels 0/+5vdc?

Yes, TTL, but that doesn't mean 0/+5V. +5V is the voltage requirement
for the TTL logic chips, logical 1 is not so high (I vaguely remember
a number of 2.4V).

> 2) Since the signal is being displayed on what essentially amounts to a TV 
> with a different input, is it safe to assume that the output is interlaced 
> in the same manner?

Not exactly. By default at least the output is non-interlaced 50/60Hz,
but of course most televisions show that without problems. Also note
that a very crude black/white composite-compatible signal is available
in the C128 RGBI output.

> 3) Are the HSYNC and VSYNC lines the same as a composite display (nothing 
> inverted or anything...just put on separate lines)?

I think so. To be certain you could check the C128 schematics.

"What's wrong, Ambassador? Don't have the guts for a fair fight?"
	-- Sinclair to G'Kar in Babylon 5:"Midnight on the Firing Line"
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