Parallax BASIC Stamp 1, Programming Manual, Page: 228 / 353

POLLOUT - BASIC Stamp Command Reference
Page 226
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BASIC Stamp Programming Manual 2.0b
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www.parallaxinc.com
The POLLOUT command achieves one of three possible actions in
response to a polled-input event. This command works in conjunction
with the POLLIN and POLLMODE commands. The following is an
example of the POLLOUT command:
POLLIN 0, 1
POLLOUT 1, 0
POLLMODE 2
Loop:
DEBUG "Looping…", CR
GOTO Loop
In this example, the POLLOUT command tells the BASIC Stamp to set I/O
pin 1 to an output mode and set it low (0) when it detects the desired poll
state. The poll state is the high (1) level on I/O pin 0 that POLLIN told it
to look for. If the polled-input pin is not high, the BASIC Stamp will set
polled-output pin 1 to high (1), instead. The BASIC Stamp will not
actually start polling until it is set to the appropriate mode, however. The
third line, POLLMODE, initiates the polling process (see the POLLMODE
description for more information). From then on, as the BASIC Stamp
executes the rest of the program, it will check for a high level (logic 1) on
I/O pin 0, in-between instructions.
Once the program reaches the endless loop, called Loop, it will
continuously print "Looping…" on the PC screen. In between reading the
DEBUG command and the GOTO command (and vice versa) it will check
polled-input pin 0 and set polled-output pin 1 accordingly. In this case,
when I/O pin 0 is set high, the BASIC Stamp will set I/O pin 1 low. When
I/O pin 0 is set low, the BASIC Stamp will set I/O pin 1 high. It will
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.
A
SIMPLE
POLLOUT
EXAMPLE
.
F
OR COMPARISON
:
ACHIEVING THE
SAME EFFECTS WITHOUT THE POLLING
COMMANDS
.
T
HE
BASIC S
TAMP
"
REMEMBERS
"
THE POLLING CONFIGURATION FOR
THE DURATION OF THE
PBASIC
PROGRAM
.