RE: VECTREX

>> Another thing I don't understand how the Vectrex 'draws' the vector. In the
>> normal vector stuff, as you all know, there is a separate 'vector
generator'
>> with it's own instruction set, RAM and ROM, vector counters ect ect. The
game
>> processor only has to send a bunch of co-ords and the vector generator will
do
>> it for it. (basically).
>
>Text display
>is done by scanning several horizontal lines in a raster pattern, the
>beam ON/OFF signal (can?) comes from a shift register that runs rather fast.
>This allows a single row of pixels for a character to be shifted out as the
>beam is scanning across. There is code for this in ROM. I think a complete
>line of text is drawn using the same 6-8 vectors for all the characters
>rather than generating a raster pattern for each character. There is
>a vectrex FAQ somewhere, and it has been emulated so there is information
>out there :-)

So, basically this means that only the beam on/off signal is corrupted here,
since the even characters are all on the same scanning (rasterized) lines.
>From the schematics you can see the Z drive signal is a demultiplexed signal
from the same single DAC who is doing all the analoge conversion (X, Y and
0ref as well).
Since the X/Y drive is all okay, I do not suspect the DAC or the bus towards
it. Therefore I shopuld be looking at the analog demux right after it, am I
right?

Even stranger; today I noticed that after power up all text is shown for about
1 second. all even characters the 'fade' away line by line very fast. Yuo can
only see this if you take out the power for a short time to be able to see the
very first second of display.

>Oh, BTW I don't remember where the vectrex shift register is, but I don't
>think it's a discrete component (this may be wrong too :)

If you are talking about the digital shifter you dicusses before, and not the
analog one splitting the analog DAC output to X Y Z and 0ref, you are right
since it is nowhere in the hardware. but in what chip could it be then? 6522?

---------------------------------------------------------------------------
** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
** message body to vectorlist-request@synthcom.com. Please direct other
** questions, comments, or problems to neil@synthcom.com.
Received on Thu Sep 14 09:59:41 2000