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Embedded Modules
© Tibbo Technology Inc.
to sustain the RTC of the EM1206 for about 5-6 days, which may appear to be
insufficient. Remember, however, that the EM1206 is a "connected" product. As
such, it can always synchronize its clock with an Internet time server or a master
clock on the main server of your system. Therefore, the role of the supercapacitor
is to provide backup power during relatively short periods of power interruption, for
example when the device is unplugged and moved to another location, or when the
device is powered off over the weekend.
It is also possible to use a 3V lithium battery for backup power. Remember,
however, that the voltage on the VCCB pin should not exceeed 2.5V. Therefore, you
need to use several diodes in series between the battery and the VCCB input. You
can calculate the time the battery will be able to sustain the EM1206 from the
average backup current, which is ~13uA. Note that the VCCB pin cosumes a much
larger current (~1mA) when the Vcc is applied and the EM1206 is running.
Therefore, your battery-based backup circuit should be designed in a way that does
not drain the battery while the Vcc is applied.
Your Tibbo BASIC/C application can access the RTC through the rtc. object (see
TIDE, TiOS, Tibbo BASIC, and Tibbo C Manual).
4.3.1.7
LED Lines
The EM1206 has two LED control lines -- Status Green (SG), and Status Red (SR).
Both lines have the same internal structure and the LEDs should be connected to
these lines as shown on the schematic diagram below. The use of an external gate
is recommended because the EM1206 has its own
are driven by SG and SR lines as well. The combined load of the internal and
external LED on the same line is too "heavy".
Further information on status LEDs can be found in
4.3.1.8
Power, Reset, and Mode Selection Lines
The EM1206 should be powered from a stabilized DC power supply with nominal
output voltage of 3.3V (+/- 5% tolerance). Current consumption of the EM1206 is
approximately 230mA (PLL on, 100BaseT mode). Providing an adequate power supply
is very important -- poorly built circuit may affect EM1206 operation. We
recommend that you use a switching power supply. One (but not the only) example
of such circuit is shown below.