Resets; Hardware Reset; Hardware Reset 1; Brown-Out Detection Reset (Hardware Reset 2) - Renesas M16C/29 Series User Manual

M 1 6 C 2 / 9 G o r u p

5. Resets

Hardware reset 1, brown-out detection reset (hardware reset 2), software reset, watchdog timer reset, and
oscillation stop detection reset are implemented to reset the MCU.

5.1 Hardware Reset

Hardware reset 1 and brown-out detection reset are available as the hardware reset.

5.1.1 Hardware Reset 1

Pins, CPU, and SFRs are reset by using the RESET pin. When a low-level ("L") signal is applied to the
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RESET pin while the supply voltage meets the recommended operating condition, pins, CPU, and SFRs
are reset (see Table 5.1 Pin Status When RESET Pin Level is "L"). The oscillation circuit is also reset and
the on-chip oscillator starts oscillating as the CPU clock. CPU and SFRs re reset when the signal applied
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to the RESET pin changes from "L" to high ("H"). The MCU executes a program beginning with the
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 content of internal RAM is undefined.
Figure 5.1 shows an example of the reset circuit. Figure 5.2 shows a reset sequence. Table 5.1 shows
status of the other pins while the RESET pin is held "L". Figure 5.3 shows CPU register states after reset.
Refer to 4. Special Function Register (SFR) about SFR states after reset.
1. Reset on a stable supply voltage
(1) Apply an "L" signal to the RESET pin
td(ROC)
(2) Wait
(3) Apply an "H" signal to the RESET pin
2. Power-on reset
(1) Apply an "L" signal to the RESET pin
(2) Increase the supply voltage until it meets the the recommended performance condition
td(P-R)
(3) Wait for
td(ROC)
(4) Wait
(5) Apply an "H" signal to the RESET pin

5.1.2 Brown-Out Detection Reset (Hardware Reset 2)

Note
Brown-out detection reset in the M16C/29 Group, T-ver. and V-ver. cannot be used.
Pins, CPU, and SFR are reset by using the on-chip voltage detection circuit, which monitors the voltage
applied to V pin.
CC
When the VC26 bit in the VCR2 register is set to 1 (reset level detection circuit enabled), pins, CPU, and
SFR are reset as soon as the voltage applied to the V
Then, pins, CPU, and SFR are reset as soon as the voltage applied to the V
above. The MCU executes the program in an address determined by the reset vector.
The MCU executes the program after detecting Vdet3r and waiting
registers are reset by the hardware reset 1 and brown-out detection reset, and are also placed in the
same reset state.
The MCU cannot exit stop mode by brown-out detection reset.
R e . v 1 1 . 2 M r a 3 . , 0 2 0 0 7
R E J 0 9 B 0 1 0 1 0 - 1 1 2
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____________
or more
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____________
or more to allow the internal power supply to stabilize
or more
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f o 4 5 8
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pin drops to Vdet3 or below.
CC
pin reaches Vdet3r or
CC
td(S-R)
ms. The same pins and
5. Resets