Re: [stella] TIA input pins 12 and 8 on PAL chips

["Mark Graybill" <saundby@xxxxxxxxxxxx>]

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)