Microcontroller grounding

[Tris20]

Ok, so I'm pretty confidant about this but a team mate has listed something different in our report and doubt has now crept in. I expect a bombardment of "OMG HOW CAN YOU NOT KNOW THAT" style comments but meh, if I get the one comment that provides the answer it's worth it right?

Anyway, when connecting a uC to some batteries and then a breadboard/pcb, am I right in saying that the negative terminal is effectively the ground. I.E. all the ground connections run back to there. NOT the GND terminal on the uC. This is connected TO the common ground but is not what actually grounds the circuit.

Need to fix this in the next hour so quick responses please!

Cheers guys!

[Rudane]

I read this a few times, and I don't see the difference. If the negative of the batteries is connected to the GND pins of the uC, then they're all at the same potential and are all ground for the circuit.
EDIT: O.K. I read it some more, and to be technically correct, the common to the circuit is the negative of the battery.

[Tris20]

Sorry, the issue I have is that they've listed pin 1(GND) as "Ground for battery" and pin 2(VIN) as "Battery Supply".

My question is really, is that accurate? I feel that listing pin1 as being responsible for grounding the battery as a bit odd. Surely it should be connection to negative terminal and connection to positive terminal respectively. Or is there a more eloquent way of putting this?

Sorry I should have made it clearer in the first post. last minute assignment fear in full flow atm.

[tszaboo]

Can we know which MCU you use? Maybe they are talking about a back-up battery for RTC and SRAM or something.

[Tris20]

Sure, NXP LPC1768

[tszaboo]

"ultra-low power Real-Time Clock (RTC) with separate battery supply" datasheet first page.
So that two pin is not for your main battery which powers everything, but a separate battery which only runs the RTC if main power is dead.

[Tris20]

Isn't that VB on pin 3?

http://mbed.org/media/img/boardlogos/lpc1768/pinout.png

[Tris20]

"EDIT: O.K. I read it some more, and to be technically correct, the common to the circuit is the negative of the battery."

Yeah this is what I thought.

Ok, gone for Pin 1:  "Ground connection to negative battery terminal".

Thanks for the help.

If a Mod sees this can you please lock the thread?

Thanks.