Hi All;

I'm designing an add-on buffered LED board for the SX 48/52 proto board, and I need to understand the reference to VCC versus VDD on the schematics.

My suspicion is that they are one-and-the-same, and simply inconsitently labeled in the published schematics, but without a physical unit to inspect, I can't be positive.

Please, can anyone who has such a board confirm that VCC is indeed the same as VDD ?

Peter,
  Vcc and Vdd both refer to a circuit's positive power supply rail.  So they would both be the same.  I hope this helps you.

Hi Chris;
Thanks for the confirmation.

Chris,
Just out of curiosity, is there some "master dictionary" of these symbols?

I understand Vin but where do the Vcc, Vdd, Vss, Vee, etc come from?  Schematics don't seem to have a "key" or "legend" like maps do.

Vss, for example is ground.  Back in the days before electricity (just kidding) did that mean something like "Short Circuit"?

John,
  While I have an extensive electronics background, especially in Digital and Microprocessor technology, I never got any college education in AC electronics, such as you would get at the end of your Engineering degree (the goos stuff)...Thusly I have heard several variations on the sources of these symbols.  I have always (Since I was into electonics) known what they mean, but the origins don't seem to be a simply answer even for engineers.  Below is a recent thread with the same question, and some possible answers.

John,
AFAIK, all these names are relics of different digital IC technologies. It all started with the "good old" TTL (Transistor-Transistor Logic) components which used Vcc (V collector-collector) for the positive supply pin and GND (ground) for the negative supply pin. Later, CMOS components came up, and Vdd (V drain-drain) was used for the positive, and Vss (V source-source) for the negative supply pin.

The "official" SX datasheets use the terms Vdd and Vss but you will find different terms in other docs.

The different names for supply pins are sometimes a PIA when you use a PCB layout program, like EGALE where library components can have implied supply pins. This means that such pins by default are not visible with the component's schematic symbols, and the software automatically "connects" such pins to equally-named nets in the schematic (if they are there). Imagine what happens when you want to use one library component with implied names Vcc and GND together with another one with implied Vdd and Vss names. Most likely, the electrical rule check wiull give you an error.

Thank you Guenther, that does help ... I'll add it to a dictionary for the SX Resource pages ... I just noticed that you first name is spelled differently on the cover of your "Programming the SX Microcontroller" book.

Obviously, at times such differences are useful.  
But, doesn't the SX-48/52 try to clairfy between the Servo power circuit and the IC only circuit?

You have created some doubts about how I wired my board for servos.

Being an antique myself,
I still prefer +5 regulated , +V unregulated , and Ground [Vss as usual].

.  
Lingusitically, these systems of jargon are often meant to exclude and confuse the layman as much as help the expert.  
For example - Long and short tons, board and cubic feet of lumber.  If you don't fully understand them, you may pay more.  Maybe a lot more.