3.58MHz clock on the TG16 expansion connector???

Started by RGB32E, June 22, 2009, 12:39:37 PM

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RGB32E

While searching for a pair of shoes I came across some sampled out RGB encoder ICs I've had for the past decade or so (pack date 10-5-98).  It got me to thinking about the replacement of the samsung encoder on the Genesis 2, and building an encoder into a turbo booster.  I've searched around for the TG16 expansion pinout, but all I can find is the pins pertaining to RGB.  Since I would like to add both "good" RGB and S-video to my turbo booster, I am wondering the following...
1.) Does the expansion port have a suitable 3.58MHz clock signal I can use for the subcarrier input on the CXA2075M (so that I can operate the IC via a native clock and avoid any chroma oscillations due to an external clock/crystal).
2.) Does anyone have any good board shots of the european TG16?  The euro TG16 contains a CXA1145, so RGB and S-Video is easy.  But, HOW is RGBS, and Subcarrier connected to the sony IC from the HU IC (ie. what components between IC A and B, if any)?

l_oliveira

You need to match the signals output by the PC-Engine graphics chip with what the video encoder expects.  (See in the data sheet)

Sony encoders are pretty much "anal" with the voltage level for their sync signal.  Wrong levels will cause it to lose sync easily (too high) or to show no image at all (too low)
In some cases you need to put a LM1881 to "clean" the signal and then use resistors to form an voltage divider to obtain proper voltage level for the video encoder.

As for the R,G and B signals 100nf capacitors are used to block any DC current and resistors are used to adjust RGB levels. It depends on the source, so if you're using it only with
the PC-engine I advice you to use adjustable pots on the prototype but then use resistors on the final assembly.

RGB32E

#2
I was hoping to get some insight on questions one and two!  :P  Let me refine...

1. Does the TG16 expansion connector carry a signal that would make a suitable 3.58MHz sub-carrier (for syncronous encoding)?  I don't have an oscilloscope...

2. Does anyone have (or can take) high rez pictures of the European TG16 PCB (especially around the CXA1145 circuit)?

RGB32E

Quote from: RGB32E on June 22, 2009, 03:01:18 PM
I was hoping to get some insight on questions one and two!  :P  Let me refine...

1. Does the TG16 expansion connector carry a signal that would make a suitable 3.58MHz sub-carrier (for syncronous encoding)?  I don't have an oscilloscope...

2. Does anyone have (or can take) high rez pictures of the European TG16 PCB (especially around the CXA1145 circuit)?

EDIT:
I think this post answers question 2... sort of... but not question 1...
http://nfggames.com/forum2/index.php?topic=172.msg1018#msg1018

l_oliveira

as for #1

http://www.gamesx.com/misctech/pcebp.php

PINS VS and VU are of unknown function but they are control bits for the video hardware.
I ran a frequency meter through the bus connector just to be sure and there were no 3.58 mhz frequency on it.

So I guess the answer is "no".

RGB32E

#5
Hmm...  Does anyone know what the minimum connections that need to be made to a CXA2075 for RGB amplification?  More specifically, do the sync and subcarrier need to be connected?  Would pin 5 on a LM1881 provide a suitable subcarrier signal, or would a crystal be required?  I would think that the sync would be needed to provide a clamp?  I recall seeing a similar info request, but I am unable to find the thread...  :-\


l_oliveira

The clamp circuit is very likely to require the csync from the PCE for it to work, even thought the device block diagram does no show it.
Besides that I don't think you need anything else if you want to use only RGB amplification.