In SX Microcontrollers, SX/B Compiler and SX-Key Tool, g_daubach wrote:

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.

---------- End of Message ----------


You can view the post on-line at:
http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=87683#m87720

Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com

The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2005 (http://www.dotNetBB.com)