USER'S GUIDE

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.

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Mitsubishi DS5000TK, DS907x SIP manual Dos