Mitsubishi Motors DS5000TK - Manual (Page 166)

USER’S GUIDE
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HIGH CURRENT DRAIN IN STOP MODE
Secure Microcontrollers draw approximately 80
µ
A of
I
CC
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
µ
A to 125
µ
A. 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 I
CC
.
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 “stuck” 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. V
CC
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.