Mitsubishi DS907x SIP High Current Drain in Stop Mode, Data is Lost or Corrupted, DOS and Donts

USER'S GUIDE

HIGH CURRENT DRAIN IN STOP MODE

Secure Microcontrollers draw approximately 80 μA of ICC in Stop mode. However, the EA pin has a resistive

load of between 40K to 125K ohms. If EA is connected to +5V, this pin will draw between 40 μA to 125 μA. This

current can be eliminated by grounding the EA pin and locking the device via the bootstrap loader. When locked, internal logic disregards the state of EA. Since it is no longer connected to +5V, the device will only draw its very low ICC.

DATA IS LOST OR CORRUPTED

A common cause is that data in a DS2250±64 or a DS5000FP based system is lost between banks. The ECE2 bit was most likely left active when software was supposed to write to CE1 memory. The opposite is also possible. When using the DS5000FP or DS2250(T) data crossing between CE1 and CE2 must be managed carefully.

Another possible cause is electrostatic discharge (ESD). This can corrupt memory locations and/or dam- age to the device. For more information see Application Note 93: Design Guidelines for Microcontrollers Incor- porating NV RAM, located in this Data Book.

INT0 IS STUCK LOW ON DS2252T

The DS2252T incorporates a DS1283 real±time clock with interrupt capability. The INTP output of the DS1283 is connected to the INTO pin of the DS5002FP micro- controller and also the INTO pin of the SIMM. If an RTC interrupt occurs, this will pull the INTO signal low.

If the system is not expecting the INTO signal to be active, this can appear as the INTO signal ªstuckº low. Because the state of the DS1283 alarm is undefined after the freshness seal is broken, the device can power up with the interrupt active, holding the INTO signal low. This condition can also occur if software accidentally activates the DS1283 alarm during normal operation, or if an alarm occurs during data retention mode. To clear this condition, clear the DS1283 alarm (if desired) as part of the power±on reset sequence.

DS5000TK KIT DOES NOT RESPOND TO KIT5K SOFTWARE

1.VCC and GND must be supplied via the ribbon cable. An external crystal (via ribbon cable) is required to

run a program. The DS5000TK hardware internal oscillator is used only for program loading.

2.Cable is broken or a standard phone cable has been used. A standard phone cable has the wrong pin out of the DS5000TK.

3.Incorrect COM port has been selected.

4.The device is not locked into its ZIF socket.

COMMUNICATION FAILS ON A DS5000TK

1.The ribbon cable represents a significant stray capacitance to the crystal pins. The crystal may be running at the wrong frequency. This can be checked by observing ALE which should be 1/6 of the crystal. If it is not, adjust the capacitors to get the correct frequency.

2.The A/B switch is in the wrong position. In position A, the serial port is routed to the target system. In position B, it goes back to the PC COM port.

DEMODS5T PROGRAM DOESN'T WORK

Normally due to the serial communication problems mentioned above. For the demo, the crystal must oscil- late at 11.0592 MHz. Also, the A/B switch must be in position B so the microcontroller communicates with the PC via the serial port while running code.

DO'S AND DON'TS

This section highlights common mistakes and offers helpful hints.

DON'TS

RC Resets

Do not use an RC circuit for a power±on reset. The Secure Microcontroller family does this internally. If the traditional RC circuit is used without a diode, it will expose the RST pin to ±5V if power falls faster than the RC time constant.

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