IF....you never have the requirement to be able to drive it the opposite = way its tied....no issues on just tying to gnd or Vcc/Vdd. =20 =20 IF you need to be able to switch the line.....and never want it floating.= ...then use a pup or pdn =20 Alot comes from experiance Harold Hallikainen wrote: > You mention that one should simply tie the pin to VDD or VSS. But what > then of the many, many schematic examples that place a single resistor > on this line? > I don't believe the resistor is necessary. Perhaps someone who does feel it is necessary can provide an explanation why. I've got several thousand units in the field where an input is just tied high or low with no problem. Inputs on chips normally have voltage limits of slightly above Vcc and slightly below Vss. Vcc and Vss seem to be within these limits. If, however, a line is bidirectional (could be an output, especially on power up prior to initialization) a resistor is appropriate to limit current during the time the line is being driven by the chip. If it's jus= t an input, though, I don't see a reason for the resistor. I'm open to comment from others, though. Harold --=20 FCC Rules Updated Daily at http://www.hallikainen.com --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist =09 --------------------------------- Do you Yahoo!? The all-new My Yahoo! =96 Get yours free! =20 --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist