User’s Manual U14272EJ3V0UM
436
APPENDIX A RESTRICTIONS ON V
R
4181
A.1 RSTSW# During HALTimer Operation
The V
R
4181 ignores the RSTSW# signal even if it is asserted while the HALTimer is operating (counting). If the
V
R
4181 is started while the RSTSW# signal is low, the RSTSW reset sequence is not executed and the V
R
4181
continues operating until the HALTimer is reset.
Consequently, the operation of the V
R
4181 may differ from the operation of the external peripheral circuits when
the RSTSW# signal is used as a reset signal to the external peripheral circuits. Particularly, when the reset signal to
a flash memory that includes a boot vector and the RSTSW# signal are shared, the V
R
4181 may not be able to read
the correct program and hang up for 4 seconds between when the V
R
4181 is started and when the HALTimer is shut
down.
[Workaround]
Do not share the reset signal to the external peripheral circuits with the RSTSW# signal.
However, if it is necessary to do so, insert a circuit like the one shown in the figure below to mask the
RSTSW# signal between when the V
R
4181 is started and when the HALTimer is cleared, by using the GPIO
pin.
Figure A-1. Mask Circuit for RSTSW# Signal
RSTSW# signal
(original)
Mask control
(GPIO, etc.)
RSTSW# signal
(for actual use)
To the V
R
4181,
flash memory, and
external peripheral circuits