MC96FR116C
November, 2018 Rev.1.8
169
When the external reset input goes high, the internal reset is released after 32ms of stability time. For
5 clock periods from the point internal reset is released, an initialization procedure is performed.
Thereafter the user program is executed from the address 0000
H
.
13.7 Brown Out Detector
The MC96FR116C includes a system to protect against low voltage conditions in order to preserve
memory contents and control MCU system states during supply voltage variations. The system is
comprised of a power-on-reset(nPOR) and an BOD with 4 voltage level indicators. The BOD is
enabled when BODEN in BODR is high. The BOD is auto-disabled upon entering STOP mode. This
auto-disable function reduces operating power noticeably consumed by BOD itself.
The BOD has two main functions. One is to generate a BOD stop level(=BODR) and the other is to
indicate voltage levels above BOD stop level denoted by BODI0,1,2,3,4 each.
Remember that BOD itself does not generate a reset signal. When operating voltage drops below a
pre-defined level(V
BODR
), the BOD does not cause the whole system to be reset, but signals main chip
to enter BOD(STOP) mode instantaneously. For more information about BOD stop, refer to section 12.
POWER MANAGEMENT.
Besides BOD stop level, the BOD gives four low voltage warning flags to indicate to the user that the
supply voltage is approaching, but is still above, the BOD stop level. These flags can be read through
the BODSR register, also can be an interrupt source when BODIEN bit in BODSR is set.
Like external reset, BODR is also filtered by a dedicated noise cancelling logic. A pulse shorter than
about 2us(typically) is ignored by the system.
INT RC OSC
ADDRESS
BUS
CORE
BUS
Main Program
Stabilization Time
TST = 32ms
?
RESETB
Release
Internal
RESETB
Release
1
2
3 4
5
?
00
01
02
?
?
?
?
?
?
? 02
RESET Process
Step
Figure 13-7 Reset procedure due to external reset input
