Parallax BASIC Stamp 2e Programming Manual page 219

T BASIC S "
HE TAMP REMEMBERS
THE POLLING CONFIGURATION FOR
PBASIC
THE DURATION OF THE
.
PROGRAM
F :
OR COMPARISON ACHIEVING THE
SAME EFFECTS WITHOUT THE POLLING
.
COMMANDS
U -
SING MULTIPLE POLLED INPUT AND
- .
POLLED OUTPUT PINS
5: BASIC Stamp Command Reference – POLLIN
continue to perform this operation, in-between each command in the loop,
endlessly.
It's important to note that, in this example, only the DEBUG and GOTO
"
commands are being executed over and over again. The first three lines of
code are only run once, yet their effects are "remembered" by the BASIC
Stamp throughout the rest of the program.
If the polling commands were not used, the program would have to look
like the one below in order to achieve the same effect.
INPUT 0
OUTPUT 1
Loop:
OUT1 = ~IN0
DEBUG "Looping...", CR
OUT1 = ~IN0
GOTO Loop
In this example, we create the inverse relationship of input pin 0 and
output pin 1 manually, in-between the DEBUG and GOTO lines. Though
the effects are the same as when using the polling commands, this
program actually takes a little longer to run and consumes 7 additional
bytes of program (EEPROM) space. Clearly, using the polling commands
is more efficient.
You can have as many polled-input and polled-output pins as you have
available. If multiple polled-input pins are defined, any one of them can
trigger changes on the polled-output pins that are also defined.
example:
POLLIN 0, 1
POLLIN 1, 1
POLLOUT 2, 0
POLLOUT 3, 0
POLLMODE 2
Loop:
DEBUG "Looping...", CR
GOTO Loop
This code sets I/O pins 0 and 1 to polled-input pins (looking for a high (1)
state) and sets I/O pins 2 and 3 to polled-output pins (with a low-active
state). If either I/O pin 0 or 1 goes high, the BASIC Stamp will set I/O
BASIC Stamp Programming Manual 2.0c • www.parallaxinc.com • Page 217
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