BASIC stamp manual v2.2

5: BASIC Stamp Command Reference – POLLIN
BASIC Stamp Syntax and Reference Manual 2.2 • www.parallax.com • Page 313
POLLIN
BS1 BS2 BS2e BS2sx BS2p BS2pe BS2px
POLLIN Pin, State
Function
Specify a polled-input pin and active state.
• Pin is a variable/constant/expression (0 – 15) that specifies the I/O
pin to use. This I/O pin will be set to input mode.
• State is a variable/constant/expression (0 – 1) that specifies
whether to poll the I/O pin for a low (0) or a high (1) level.
Quick Facts
Table 5.73: POLLIN Quick Facts.
BS2p, BS2pe, and BS2px
Available
actions in
response to
reaching the
desired State
1) Nothing,
2) Set polled-output pins to a specified state,
3) Run another program (in a specified program-slot),
4) Wait (pause program execution) until desired State is reached,
5) Any combination of 2, 3 and 4, above.
Special notes
• The polled-input pins are monitored (polled) in-between each command
within the PBASIC code.
• On the BS2p40, polled-input pins can be defined on both Main I/O and
Auxiliary I/O pins. These are all active regardless of which group the
program happens to be using at the time of a polling event.
Useful SPRAM
locations
Locations 128 – 135 hold polled interrupt status. See Table 5.77 in the
POLLMODE command section for more information.
Related
commands
POLLMODE, POLLOUT, POLLRUN and POLLWAIT
Explanation
The POLLIN command is used to specify an input pin to monitor, or
"poll", in-between instructions during the rest of the PBASIC program.
The BASIC Stamp will then perform some activity (in-between
instructions) when the specified State is detected. The activity performed
depends on the POLLMODE, POLLOUT and POLLRUN commands.
The "polling" commands allow the BASIC Stamp to respond to certain I/O
pin events at a faster rate than what is normally possible through manual
PBASIC programming. The term "poll" comes from the fact that the
BASIC Stamp module’s interpreter periodically checks the state of the
designated polled-input pins. It "polls" these pins after the end of each
PBASIC command and before it reads the next PBASIC command from the