CXA2075M RGB encoder question on the SYNCIN signal

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CXA2075M RGB encoder question on the SYNCIN signal

Postby unebonnevie » Thu Jan 14, 2016 10:31 pm

Hi,

Please explain what kind of signal input to the CXA2075M RGB encoder's pin 10, the SYNCIN? Is it a toggle input, that is, off/on? Greatly appreciate it if you could point me to the code to further understand how the input signal to the SYNCIN pin is generated. Thank you!
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Re: CXA2075M RGB encoder question on the SYNCIN signal

Postby unebonnevie » Sat Jan 16, 2016 4:52 pm

unebonnevie wrote:Hi,

Please explain what kind of signal input to the CXA2075M RGB encoder's pin 10, the SYNCIN? Is it a toggle input, that is, off/on? Greatly appreciate it if you could point me to the code to further understand how the input signal to the SYNCIN pin is generated. Thank you!


Also, 2nd part to my question: Why the 7404 is used with the SYNCIN pin?

Thank you!
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Re: CXA2075M RGB encoder question on the SYNCIN signal

Postby simon » Sun Jan 17, 2016 6:15 pm

SYNCIN is the input for a composite sync signal with TTL level voltage. This signal is generated by the VDP.
The 7404 has nothing to do with this signal. I just made my drawing a bit unclear. What I did is to ground every input of unused 7404 gates. Thus they are not flowing around and prevent them from accidentally oscillating.

Simon
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Re: CXA2075M RGB encoder question on the SYNCIN signal

Postby unebonnevie » Wed Jan 20, 2016 6:47 pm

simon wrote:SYNCIN is the input for a composite sync signal with TTL level voltage. This signal is generated by the VDP.


Thank you. And sorry for such a noob question here, but, the composite sync signal here refers to which part of the NTSC or PAL signal? I am trying to see if I can generate such signal using a micro-controllers. Below is a link to an image showing the NTSC signal.

http://belogic.com/uzebox/images/ntsc-signal.gif
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Re: CXA2075M RGB encoder question on the SYNCIN signal

Postby simon » Thu Jan 21, 2016 1:13 pm

This seem to be a BAS signal. This should be fed directly to the SYNCIN. BUT: It doesn't make much sense to me if your signal is (F)BAS already.
You might want to read the CXA2075M Datasheet for more detailed information.

Simon
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