Hello Mark,
I have discussed this topic with someone else in the meantime and I
suggested to replace the whole circuitry at TIA input pins 8 & 12 by a
common 4,43MHz TTL oscillator (e.g. a TCXO in a DIP14 package), leaving pin
12 unconnected. Do you know if this might work too?
With best regards,
Matthias Hartl
----- Original Message -----
From: Mark Graybill
To: stella@xxxxxxxxxxx
Sent: Monday, December 02, 2002 6:36 AM
Subject: Re: [stella] TIA input pins 12 and 8 on PAL chips
I would expect that it uses a series of gates as a delay line for the phase
changes. The delay of the gate would be a phase change equal to the part of
the cycle time that the delay takes. The signal doesn't have to be a sine
wave at output, a square wave that is phase-shifted would have the same
effect.
-Mark G.
----- Original Message -----
From: Matthias Hartl
To: stella@xxxxxxxxxxx
Sent: Wednesday, November 27, 2002 2:35 PM
Subject: [stella] TIA input pins 12 and 8 on PAL chips
Hello,
Ok, this is question is not related to programming the Stella chip, but I
hope someone is willing and able to answer it anyway. I'm currently
assembling my own ATARI 2600 clone wit a PAL version of the TIA chip.
Everything works fine so far (black & white). In order to get some color
onto my tv screen, I have to apply a certain "signal" to pin 8 and 12,
labeled as PALS and PALI in the schematics found at atariage.com. My humble
electronic skills tell me this is some kind of sine wave at a frequency of
4,43MHz. Is this right? How does the TIA do the necessary phase shift in
order to encode the color information?
I would be very glad, if someone could spread some light on this. Thank you
in advance!
Matthias Hartl (Germany)
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