PINS - DIRS

[JackMan]

What's the result of eliminating the typical PINS - DIRS code on initialization? I've written quite a few of my own programs and have never included this, all have worked fine.

[JonnyMac]

It will of course depend on the program.  Most of the time you will "get away with it" but in some cases you won't -- depends on hour you're using pins.  For example, I don't like to use HIGH and LOW to turn pins on and off.  Why?  Because there are active-low circuits in the world and I prefer to write code like this:

  MyOutput = IsOff

In order for that to work, however, the DIRS bit for that pin must be pre-set (HIGH and LOW do this internally).

Most of my programs start out like this:

Reset:
  PINS = %00000000
  DIRS = %00111111

This allows me a place to jump back to and reset all IO to a known state.

In the end, I'm a very conservative programmer; this stems from years of developing products/programs for public consumption and needing them to be as "bullet proof" as possible.

[JackMan]

Good answer. I do use HIGH - LOW in my programs. I have also successfully used IsOff - IsOn for trigger input without including PINS - DIRS in initialization. Does this work because that particular PIN is being used as an input?

[JonnyMac]

Yes; when the BASIC Stamp resets all pins are defined as inputs.  Technically, you only have to define outputs -- using the DIRS register lets you setup all IO pins in one line of code.