357
Programmable Hardware Manual (PHM)
© Tibbo Technology Inc.
Control lines
This Tibbit has four control lines:
·
-SDWN (shutdown): When LOW, turns off the Tibbit's power regulators. When the
line is switched to HIGH, the power regulators are enabled, but the modem
remains off.
·
PWRKEY (power key): A LOW-to-HIGH transition on this line toggles the power on
and off; it turns the modem on if it was off, or off if it was on. Toggling the
module on requires keeping a HIGH state of signal (after a transition from LOW) for
about 500ms. Turning the module off requires keeping a HIGH state for about 2.5
seconds. The two following figures illustrate the process of turning the modem on
and off.
Turning the modem on
Turning the modem off
·
STATUS: This line is LOW when the modem is off and HIGH when it is on. This line
can be used to check the current power state of the modem. It takes at least 22
seconds for the STATUS line to reach HIGH after the modem is powered on, after
which the module can begin operating. There are two methods of determining
whether the modem is on or off: by sending an AT command and checking for a
response or querying the STATUS line's state. Note that the line's state is
undetermined when the modem is shut down (i.e., the -SDWN line is LOW).
·
RESET: Bringing this line HIGH for about one second resets the modem. There is
no need to reset the modem after turning on its power.