Schematic considerations for MSP430?

Jul 19, 2004 3 Replies
C

I know that I've seen a TI document about this before, but a 15 minute google search left me with nothing.



I am double-checking a schematic that uses an MSP430F149, and I want to ensure that I have all the pins correctly terminated for (1) correct operations and (2) access to the JTAG port for in-circuit programming and debugging. Here's what I've got:



AVcc -- 3.3V DVcc -- 3.3V DVss -- GND AVss -- GND XIN -- GND VeRef+ -- GND VeRef- -- GND RST -- Pulled up to 3.3V, with a connector at pin TCK -- Connector at pin TMS -- Connector at pin TDI -- Connector at pin TDO -- Connector at pin



Everything else is open (except for some inputs and outputs that I am using). I am using the internal oscillator as clock.



Any help (whether a reference to a document or a check of my pinout) will be greatly appreciated.


-Chess


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D

Hi,

TI have a demo board based on the msp430f149, you can check all the connections against that.

I'm not sure it's schematic is on the web, but i could dig it out for you if your having problems finding it.

Dave

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M

Not sure about tying RST high. TI's demo schems always use an RC reset in the range 10K-100K (though I think 30K is the "upper limit" according to other documentation) + 100n, and this works in the lab. The MSP's hardware brownout does leave a hole however, so I would recommend an external reset chip as best practice.

You can leave VeRef+ floating. I'd be tempted to do the same with XIN, it might be biassed.

Most of the demo files have a ASCII schematic in a big comment at the top.

Regards, Mike.

Mike Page BEng(Hons) MIEE www.eclectic-web.co.uk Quiet! Tony's battling the forces of conservatism, whoever we are.
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C

Thank you for the offer, but I do have that schematic. The things that I noticed about it is that it has a filter capacitor on the DVcc and AVcc lines, and that it actually connects the XOUT pin to the JTAG port.

I have added a capacitor to mine (100nF ceramic), put have not put a lead on XOUT, because I read elsewhere on USENET That this pin is no longer necessary.

-Chess

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