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M16C/62P Group (M16C/62P, M16C/62PT)
5. Reset
Hardware reset 1, voltage down detection reset (hardware reset 2), software reset, watchdog timer reset
and oscillation stop detection reset are available to reset the microcomputer.
5.1 Hardware Reset 1
The microcomputer resets pins, the CPU and SFR by setting the RESET pin. If the supply voltage meets
the recommended operating conditions, the microcomputer resets all pins when an "L" signal is applied to
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the RESET pin (see Table 5.1 Pin Status When RESET Pin Level is "L"). The oscillation circuit is also
reset and the main clock starts oscillation. The microcomputer resets the CPU and SFR when the signal
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applied to the RESET pin changes low ("L") to high ("H"). The microcomputer executes the program in an
address indicated by the reset vector. The internal RAM is not reset. When an "L" signal is applied to the
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RESET pin while writing data to the internal RAM, the internal RAM is in an indeterminate state.
Figure 5.1 shows an example of the reset circuit. Figure 5.2 shows a reset sequence. Table 5.1 lists pin
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states while the RESET pin is held low ("L"). Figure 5.3 shows CPU register states after reset. Refer to 4.
SFR for SFR states after reset.
5.1.1 Reset on a Stable Supply Voltage
(1) Apply "L" to the RESET pin
(2) Apply 20 or more clock cycles to the XIN pin
(3) Apply an "H" signal to the RESET pin
5.1.2 Power-on Reset
(1) Apply "L" to the RESET pin
(2) Raise the supply voltage to the recommended operating level
(3) Insert td(P-R) ms as wait time for the internal voltage to stabilize
(4) Apply 20 or more clock cycles to the XIN pin
(5) Apply "H" to the RESET pin
5.2 Voltage Down Detection Reset (Hardware Reset 2)
The microcomputer resets pins, the CPU or SFR by setting the built-in voltage detect circuit. The voltage
detect circuit monitors the voltage applied to the VCC1 pin.
When the VC26 bit in the VCR2 register is set to "1" (reset level detect circuit enabled), the microcomputer
resets pins, the CPU and SFR as soon as the voltage that is applied to the VCC1 pin drops to Vdet3 or
below.
Then, the microcomputer initializes pins, the CPU and SFR as soon as the voltage to the VCC1 pin reaches
Vdet3r or above. The microcomputer executes the program in an address determined by the reset vector.
The microcomputer executes the program td(S-R) ms after detecting Vdet3r. The same pins and registers
are reset by the hardware reset 1 and voltage down detection reset (hardware reset 2) , and are also placed
in the same reset state.
The microcomputer cannot exit stop mode by voltage down detection reset (hardware reset 2) .
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page 31
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5. Reset
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