R01UH0136EJ0210 Rev.2.10
Page 53 of 800
Jul 31, 2012
M16C/64A Group
6. Resets
6.4.2
Hardware Reset
This reset is triggered by the
RESET
pin. When the power supply voltage meets the recommended
operating conditions, the MCU resets the pins, CPU, and SFRs when a low-level signal is applied to the
RESET
pin.
When changing the signal applied to the
RESET
pin from low to high, the MCU executes the program
at the address indicated by the reset vector. fOCO-S divided by 8 is automatically selected as the CPU
clock after reset.
The HWR bit in the RSTFR register becomes 1 (hardware reset detected) after hardware reset. Refer
to 4. “Special Function Registers (SFRs)”
for the remaining SFR states after reset.
The internal RAM is not reset. When a low-level signal is applied to the
RESET
pin while writing data to
the internal RAM, the internal RAM becomes undefined.
The procedures for generating a hardware reset are as follows:
When the power supply is stable
(1) Apply a low-level signal to the
RESET
pin.
(2) Wait for tw(RSTL).
(3) Apply a high-level signal to the
RESET
pin.
When the power is turned on
(1) Apply a low-level signal to the
RESET
pin.
(2) Raise the power supply voltage to the recommended operating level.
(3) Wait for td(P-R) until the internal voltage stabilizes.
(4) Wait for
×
20 cycles.
(5) Apply a high-level signal to the
RESET
pin.
Figure 6.4 shows an Reset Circuit Example.
Figure 6.4
Reset Circuit Example
1
fOCO S
–
----------------------
RESET
RESET
0 V
0 V
Recommended
operating
voltage
td(P-R) +
×
20 cycles or above
1
fOCO-S
VCC1
VCC1
0.2 VCC1 or below
0.2 VCC1 or below
Note:
1. When VCC1 > VCC2, make sure that the VCC2 voltage is lower than that of VCC1 when the power is
turned on or off.
Содержание M16C/60 Series
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