Mitsubishi Motors DS5000TK - Manual (Page 167)

USER’S GUIDE
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Battery backed signals
Do not connect lithium backed chip enables or signals to
non–backed devices. This produces a drain on the lith-
ium cell. On the DS5001 and DS5002, PE1 and PE2 as
a well as CE1 – 4 are lithium backed. PE3 and PE4 are
not backed and can be connected to normal circuits. On
the DS5000FP, CE1, CE2, and BA14 are lithium
backed.
Negative Voltage Spikes
Do not allow negative voltage to contact the device. This
includes under shoots on power or ports, static, plug-
ging in backwards, or applying a signal without a com-
mon ground reference. Electrostatic Discharge can also
produce momentary negative voltages.
DO’S
Use Static Protection
Do use Schottky diodes and resistors on port pins that
are available at the outside world. Static can represent a
negative voltage that temporarily collapses the battery
voltage. This is discussed in Application Note 93,
Design Guidelines for Microcontrollers Incorporating
NV RAM.
Use the Loader Port
Do provide a method of in–system loading such as an
RS232 transceiver, a connector, and a way to invoke
the loader. This is especially important to applications
that are encased in epoxy.
Use the Watchdog
All microprocessor systems encounter situations that
they can not deal with by design. The Watchdog is the
first line of defense. If software runs out of control, it can
only do so for the duration of one Watchdog time–out.
Control power supply
An ideal situation is when the microprocessor controls
the power down function. If the power switch actually
asks software to turn off the power, then software is
never taken by surprise. Also, make certain that the
power supply slew rate meets the value specified in the
specific data sheet.