Re: Tempest Tech?? (Using the Z input on scope with Tempest)

Ouch!

You are right. I just used negative (or positive if you look at it from
the blanking side) logic
on the RGB outputs (active low, blanked high), but ofcourse they are
not. If 'More positive
means more of that color', then a NOR is the right device.

Cya !

(Well, I am not sure wether this is still 'ON TOPIC' or not, just
because a Vector games uses
TTL...) :)

Cya !

Joel Rosenzweig wrote:
>
> I think you might be confusing your logic functions. Consider the following:
>
> Suppose R and B are high, G low. (You want the trace to display, with a
> negative Z input. Z high = BLANK, Z low = "Show me the vectors!")
> NAND(R,G,B) is TRUE, so your display will BLANK. However, you'd like the
> output of your equation to be FALSE, so that the display will be ON.
>
> The only time the NAND gate would give the right signal would be if all
> three inputs were HIGH. But that condition only happens when the game draws
> WHITE on the screen.
>
> Think of it this way. You'd like the display to be blanked when all of the
> outputs are low. So, you'd like some function that says F(R,G,B) = HIGH
> when R=G=B = LOW, and F(R,G,B)= LOW for all 7 other combinations. In
> English, it says "If none of my R,G,B output lines are driving the monitor
> at this time, blank the display. If any of my R,G,B output lines are
> driving the monitor, turn on the display." A NOR gate happens to be
> function that gives us these operating characteristics. It has the following
> truth table:
>
> R G B F(X)
> --------------
> 0 0 0 1 (BLANK the display)
> 0 0 1 0 (ENABLE the display)
> 0 1 0 0 (ENABLE the display)
> 0 1 1 0 (ENABLE the display)
> 1 0 0 0 (ENABLE the display)
> 1 0 1 0 (ENABLE the display)
> 1 1 0 0 (ENABLE the display)
> 1 1 1 0 (ENABLE the display)
>
> Joel-
>
> >Hmm.. Lets give this a second thought:
> >
> >If the vector drawn should be RED, and you use an OR port to BLANK
> >the trace, the BLUE vector would become BLACK (blanked), because the
> >BLUE (and the green)
> >output will be blanked (and thus the output of the OR would blank the
> >vector on a
> >monochrome display).
> >
> >The (retrace) vectors should only be black when ALL of the outputs are
> >blanked, so
> >you should use an AND port (or NAND, if your scope has an inverted Z
> >input).
> >
> >Am I right or do I forget something?
> >
> >Cya !
> >
> >Joel Rosenzweig wrote:
> >>
> >> Matt,
> >>
> >> Scott's suggestion is OK, but there's a little more the to story. If you
> >> use only one of the RGB signals as your Z input, you will only see
> vectors
> >> that use the corresponding color gun to greate the vector. That is, if
> you
> >> hook up only your B gun and Tempest draws a magenta vector, you'll see it
> >> because the B and R guns are used to create magenta. But if Tempest
> draws a
> >> green vector you'll miss it because your scope is blanking on everything
> >> except B gun activity.
> >>
> >> In order to see all of the vectors, you must OR all three signals
> together.
> >> If you scope needs an inverted input on Z, remember to invert the output.
> >> That is, use a 3 input NOR gate or logically equivalent circuit.
> >>
> >> Joel-
> >>
> >> >Matt,
> >> > Use any one of the three RGB signals as the z input to a scope.
> Tempest
> >> >has a mono Z out on Q10(i think) Q10 combines the three RGB signals into
> >> >one mono signal, perfect for an o-scope.
> >> >
> >> >-Scott
> >> >
> >> >PS please re-post this to the VL if it doesn't show-up. My VL posts
> don't
> >> >bounce, but they never appear on the VL.
> >> >
> >> >At 04:38 PM 12/6/99 -0800, Matt Rossiter - Verio Southern California
> wrote:
> >> >>You can also hook the board up to an oscilloscope if it has an XY mode.
> >> >>This is how I test all my vector boards from home.
> >> >>
> >> >>Of course, this brings up another question I have. I hope I'm not
> asking
> >> >>too many questions. How does one hook up the Z or blanking circuit to
> the
> >> >>oscilloscope? I know with black and white vector games there's a Z
> >> >>hookup, but I can't see any for the color vector games but I do see X
> and
> >> >>Y Inverts. Could someone explain this to me?
> >> >>
> >> >>
> >> >>Matt
> >> >
> >> >--
> >> >Scott Swazey QUALCOMM Incorporated Work: (858) 657-2419
> >> >mailto:sswazey@qualcomm.com V-213G Pager:(858) 683-5210
> >> >
> >> >
> >
> >
Received on Tue Dec 7 15:42:06 1999