BASIC stamp manual v2.2

NAP – BASIC Stamp Command Reference
Page 286 • BASIC Stamp Syntax and Reference Manual 2.2 • www.parallax.com
the actual timing to vary by as much as –50, +100 percent (i.e., a Duration
of 0, NAP can range from 9 to 36 ms). At room temperature with a fresh
battery or other stable power supply, variations in the length of a NAP
will be less than ±10 percent.
One great use for NAP is in a battery-powered application where at least a
small amount of time is spent doing nothing. For example, you may have
a program that loops endlessly, performing some task, that pauses for
approximately 100 ms each time through the loop. You could replace your
PAUSE 100 with NAP 3, as long as the timing of the 100 ms pause was
not critical. The NAP 3 would effectively pause your program for about
144 ms and, at the same time, would place the BASIC Stamp in low-power
mode, which would extend your battery life.
If your application is driving loads (sourcing or sinking current through
output-high or output-low pins) during a NAP, current will be interrupted
for about 18 ms (60 µs on the BS2pe) when the BASIC Stamp wakes up.
The reason is that the watchdog-timer reset that awakens the BASIC
Stamp also causes all of the pins to switch to input mode for
approximately 18 ms (60 µs on the BS2pe). When the interpreter firmware
regains control of the processor, it restores the I/O direction dictated by
your program.
If you plan to use END, NAP, POLLWAIT or SLEEP in your programs,
make sure that your loads can tolerate these power outages. The simplest
solution is often to connect resistors high or low (to +5V or ground) as
appropriate to ensure a continuing supply of current during the reset
glitch.
The demo program can be used to demonstrate the effects of the NAP
glitch with an LED and resistor as shown in Figure 5.18.
A GREAT USE FOR NAP; FREE POWER
SAVINGS
.
T
IPS FOR DRIVING LOADS DURING NAP.