NC7WZ07P6XTR-ND Buffer- what is its purpose? MC Audio BOard Topic is solved

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xlordofpainx
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NC7WZ07P6XTR-ND Buffer- what is its purpose? MC Audio BOard

Postby xlordofpainx » Thu May 17, 2018 9:24 am

Hey guys, I am trying to understand what the NC7WZ07P6XTR-ND
is used for - I see that it is a buffer, but why is it needed.
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mon2
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Postby mon2 » Thu May 17, 2018 10:15 am

Hi. An open drain output allows multiple outputs (each must be also open drain) to be tied together. The output must have a pull up resistor present.

The other type of digital logic output is push-pull which cannot share the output pins.
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xlordofpainx
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Postby xlordofpainx » Thu May 17, 2018 11:30 am

So a PG signal is sent to the sequencer - it introduces a delay and then send the Power in Reset which we would want to tie together with the possible Reset when connected to the X-tag? And there would not be any other way to tie the RST lines unless I apply the buffer circuit?

Also about the sequencer. Why is it needed. It would only seem logical that you would like a delay after the core receives full 1V before putting the RST pin to 0, but I do not have a technical explanation for it. My other thought was the sequencer is just needed to produce a pulse as the RST should be constantly 0 during work, but to actually reset you would need a pulse to 1.
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Postby mon2 » Thu May 17, 2018 11:53 am

Review the exact truth table for part used in the design. The part will output a logic low while the input voltage is under the 1 volt level. Once the threshold is reached, the output will be high-z (open; high impedance). The external pull up resistor will soft pull up to a high level. The XMOS cpu will remain in reset state if the pin is LOW.

The outputs of these buffers are tied together so that the XTAG tool can also perform a reset at anytime. This is only possible as shown due to the open drain outputs.

Once the voltage level is met, there is a delay and then the buffer becomes open to release the cpu out of reset.
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xlordofpainx
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Postby xlordofpainx » Thu May 17, 2018 12:58 pm


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