# Application of buffer chip in serial communication

On a microcontroller board that I am working on, there is a buffer chip between the microcontroller TI msp430 F1611 and USB interface FTDI FT232BL. The chip is named NC7WZ126.

My question is, why they have used that buffer? what benefits it has and what would happen if that chip was not there at all?

I am asking this because I want to wire up directly to TX/RX pins of the msp430 for some debugging purpose. So should I directly wire to the msp430 pins (Pins #34 and #35)? Or I should wire to the inputs of the buffer (pin 2 and 3 of NC7WZ126)

UPDATE

AFAIK msp430 is using 0-3.3V for low-high (Since its get its Vcc after a 3.3 regulator) bits and that FTDI is 5 Volts (powered by USB) so can be that a reason for that buffer? Considering That I want to feed in 5V CMOS to RX/TX of msp 430, then I should wire to the buffer and not to the 430?

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Yes, the buffer is performing logic level translation. I know I've answered this exact question before, but I doubt that I can find that other one now. –  Dave Tweed Dec 22 '12 at 1:34
possible duplicate of 74LVC1G125 on the arduino wireless shield? –  Dave Tweed Dec 22 '12 at 1:39
Actually, it's the exact same answer to a different question. There's no way you would have found this answer based on what you were looking for. –  Dave Tweed Dec 22 '12 at 1:40
@DaveTweed Thanks that also applies! –  Sean87 Dec 22 '12 at 1:48
I agree that the purpose of that chip is probably to do level shifting, but that is a bit strange, because the FT232 can easily operate its uC-side pins at 3v3. –  Wouter van Ooijen Dec 22 '12 at 7:58

Without looking at the details, you should be able to figure that out once you read this and then go get the datasheets.

THere are three reasons to buffer:

1) to do the voltage translation from one domain to another. - is the msp430 running at a different voltage that what the USB is specified for?

2) The driver provides higher current drive for a higher load. - often the pins are limited drive (current capability)

3) to protect the more expensive part which might be more sensitive to ESD etc. - added for completeness

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Thanks for quick answer...I updated my question, can you check please? –  Sean87 Dec 22 '12 at 1:31
I would say that was the reason ... –  placeholder Dec 22 '12 at 1:33