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?
Best Answer
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