I am starting to believe that when I first attempted to build a LM1881 circuit for stripping sync from NTSC video, that perhaps I was not using the correct/all the pins.
(http://www.gamesx.com/grafx/lm1881.gif)
Here's a diagram of the chip and all of its pins. I used pins 1, 2, 4 [ground] and 8, but I didn't use pin #6 which is labeled as "Rset" According to the description I need to be using that pin. What is it, and why do I need to be using it? Do I need to use any other pins that I am not aware of? I thought that simply plugging in the NTSC video line (with cap) then ground and power and finally composite sync would do the job, but perhaps I was wrong?
Thanks for the help!
EDIT: If you wouldn't mind, I would also like to know the function of pins that aren't used for simple sync-stripping.
You have to connect those two components to pin 6 as well, the rest of them you can safely ignore.
When hooking those up, I usually just solder them over the top of the chip to connect them to pin 4. Keeps the whole thing nice and tidy.
Quote from: Lawrence on June 09, 2009, 09:56:53 AM
You have to connect those two components to pin 6 as well, the rest of them you can safely ignore.
When hooking those up, I usually just solder them over the top of the chip to connect them to pin 4. Keeps the whole thing nice and tidy.
Just to clarify, I will need to connect Composite video and Composite sync to this "Rset" pin? Then from "Rset" I bring one wire to the ground? Would I also need to bring the ground wire from the SNES console that ground pin as well?
Thanks for your patience!
According to the diagram, the only thing you should be connecting to Rset is GROUND, through a capacitor and a resistor.
Quote from: Lawrence on June 09, 2009, 02:05:01 PM
According to the diagram, the only thing you should be connecting to Rset is GROUND, through a capacitor and a resistor.
Interesting indeed. May I inquire as to what the "Rset" function is? I feel like such a goomba for not doing this in the very first place.
I never bothered to work out its function, I just hooked it up as instructed and enjoyed the result. =)
Quote from: zedrein on June 10, 2009, 06:40:27 AM
Quote from: Lawrence on June 09, 2009, 02:05:01 PM
According to the diagram, the only thing you should be connecting to Rset is GROUND, through a capacitor and a resistor.
Interesting indeed. May I inquire as to what the "Rset" function is? I feel like such a goomba for not doing this in the very first place.
Placing different value resisters on the Rset pin changes which scanning frequency the LM1881 operates at. (From Application Notes http://www.national.com/ds/LM/LM1881.pdf )
My heavens! I am so excited at the prospects of playing my SNES in glorious RGB that I may need to be sedated. Lawrence [and anyone else for that matter] please tell me what sorta' shock I'm in for so I don't end up collapsing when I first experience gaming visually perfected!