8 to 1 scart switch

[@xi@g@me]

Hi all,
I'm thinking about building my own 8 to 1 SCART switch (for the PAL format, in France), supporting both RGB & CBVS, in order to have all my retro game consoles connected to the TV without having to remove / change / re-plug cables each time.
One of the reasons is that commercial devices are either expensive either not with 8 inputs (and cascading several is ugly to the eye).

Anyway, I started some research on how to do such a thing, and I found this schematic, using the MAXIM MAX9655 chip :

https://www.maximintegrated.com/en/images/appnotes/4522/4522Fig03.gif

I had a look at the datasheet, and all seems to be doing what I want, but as it does only work for 2 inputs, I'm wondering if it would be a safe thing to casacade such ICs (in a way there is always 3 MAX9655 between any input and the output), while keeping a good signal and not to much delay ?

Thanks in advance for your tips

 

[kellys_eye]

You would have to 'parallel' the outputs to get eight-into-one but the safest way would be via an 'enable' signal on the MAX device. Clearly it doesn't have one so this would need to be implemented at the output - any device that could 'pass' the signal but be enabled/disabled and driven through an 3-of-8 decoder would work.

 

[@xi@g@me]

It seems like the MAX 9656 has such an output enable pin (the outputs are as 3 state buffers in the datasheet). The other functionality it offers is not useful for me, but shouldn't prevent me from doing what I need.
what do you mean by "parallel" the outputs ? Do I really need to be able to hi-Z some outputs ?
The intended goal is to have 4 MAXs for the 8 inputs, put the 4 outputs to 2 other MAXs, and finally the 2 output to a last one, and towards the TV (like some kind of bintree).

 

[kellys_eye]

If you wish to cascade them then the 'parallel' solution proffered is not required and cascading seems perfectly 'do-able'.

 

[@xi@g@me]

Yeah thanks But still, what did you mean by "parallel" solution ?

 

[kellys_eye]

The parallel solution was what I initially proposed (but requiring the /EN signals from a 3-of-8 decoder).

 

[@xi@g@me]

Oh, you meant using tri-state buffers for each input, and selecting which one can pass using the decoder ? Is there no risk for the signal to be altered using these ?
With something like this for each input :
http://www.ti.com/product/SN74LS243

 

[@xi@g@me]

Someone gently reminded me the parts I'm showing here (MAX9655 & MAX9656) are no longer available for sale I'll have to find another way of doing what I want

 

[@xi@g@me]

I finally managed to break open an old SCART switch, and it seems that simple relays may be largely sufficient (they use mechanical switches with 12 contacts at once). So adios the MAX4399 or MAX9655 thanks for your help, I'll post the schematics here once I'm done