BASIC stamp manual v2.2

4: BASIC Stamp Architecture – PIN Symbols

BASIC Stamp Syntax and Reference Manual 2.2 • www.parallax.com • Page 101

' {$PBASIC 2.5}

signal PIN 2 ' pin-type symbol representing I/O 2

OUTPUT signal ' set signal pin to output

signal = 1 ' set signal high

The OUTPUT command treats signal as a constant equal to 2 and the

signal = 1 statement treats signal as a variable equal to the output variable

for the defined pin (OUT2 in this case).

You might be wondering why “signal = 0” in the IF…THEN statement of

our first example treats signal as the input variable IN1 and yet “signal =

1” in our last example treats signal as the output variable OUT2. The

distinction is that the first example is a comparison and the second

example is an assignment. Comparisons need to “read” expressions and

then evaluate the comparison while assignments need to read expressions

and then “write” the results. Since signal is to the left of the equal sign (=)

in our assignment statement, it must be a variable we can write to, thus it

must be treated as OUT2, in this case.

What happens if our pin-type symbol is to the right of the equal sign in an

assignment statement? Example:

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signal1 PIN 1 ' pin-type symbol representing I/O 1

signal2 PIN 2 ' pin-type symbol representing I/O 2

INPUT signal1 ' set signal1 pin to input

OUTPUT signal2 ' set signal2 pin to output

signal2 = signal1 ' set signal2 pin to signal1 pin’s state

In this case signal2 is treated as OUT2 and signal1 is treated as IN1; left side

must be written to and right side must be read from.

If a pin-type symbol is used in a command, but not in the Pin argument of

that command, it will be treated as an input variable (i.e.: INx). NOTE: It

is very rare that you’ll need to use a pin-type symbol in this way.

The following is a summary of behaviors and uses of pin-type symbols.

All