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M16C/29 Group
5. Reset
There are four types of resets: a hardware reset, a software reset, an watchdog timer reset, and an oscilla-
tion stop detection reset.
5.1 Hardware Reset
There are two types of hardware resets: a hardware reset 1 and a hardware reset 2.
5.1.1 Hardware Reset 1
A reset is applied using the RESET pin. When an "L" signal is applied to the RESET pin while the
power supply voltage is within the recommended operating condition, the pins are initialized (see
Table 5.1.1.1 Pin Status When RESET Pin Level is "L"). The on-chip oscillator is initialized and used
as sysem clock.
When the input level at the RESET pin is released from "L" to "H", the CPU and SFR are initialized,
and the program is executed starting from the address indicated by the reset vector. The internal RAM
is not initialized. If the RESET pin is pulled "L" while writing to the internal RAM, the internal RAM
becomes indeterminate.
Figure 5.1.1.1 shows the example reset circuit. Figure 5.1.1.2 shows the reset sequence. Table
5.1.1.1 shows the status of the other pins while the RESET pin is "L". Figure 5.1.1.3 shows the CPU
register status after reset. Refer to "SFR Map" for SFR status after reset.
1. When the power supply is stable
(1) Apply an "L" signal to the RESET pin.
(2) Wait td(ROC) or more.
(3) Apply an "H" signal to the RESET pin.
2. Power on
(1) Apply an "L" signal to the RESET pin.
(2) Let the power supply voltage increase until it meets the recommended operating condition.
(3) Wait td(P-R) or more until the internal power supply stabilizes.
(4) Wait td(ROC) or more.
(5) Apply an "H" signal to the RESET pin.
5.1.2 Hardware Reset 2
Note
5.1.2 Hardware Reset 2 is described in the Normal-ver. only as an example.
Do not use this function in the T-ver. and V-ver.
This reset is generated by the microcomputer's internal voltage detection circuit. The voltage detec-
tion circuit monitors the voltage supplied to the V
If the VC26 bit in the VCR2 register is set to "1" (reset level detection circuit enabled), the microcom-
puter is reset when the voltage at the V
Conversely, when the input voltage at the V
SFR are initialized, and the program is executed starting from the address indicated by the reset
vector. It takes about td(S-R) before the program starts running after Vdet3 is detected. The initialized
pins and registers and the status thereof are the same as in hardware reset 1.
Rev.1.00 Nov 01,2004
REJ09B0101-0100Z
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page 28 of 402
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pin.
CC
input pin drops below Vdet3.
CC
pin rises to Vdet3 or more, the pins and the CPU and
CC
5. Reset
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