M32C8A Datasheet, PDF (50/372 Pages) Renesas Technology Corp – RENESAS MCU M16C FAMILY / M32C/80 Series

M32C/8A Group
5. Reset
5. Reset
Hardware reset 1, hardware reset 2 (Vdet3 detection function), software reset and watchdog timer reset are
implemented to reset the MCU.
5.1 Hardware Reset 1
Pins, CPU, and SFRs are reset by using the RESET pin. When a low-level (“L”) signal is applied to the RESET pin
while the supply voltage meets the recommended operating conditions, ports and I/O pins for peripheral functions
are reset. (Refer to Table 5.1 Pin states while RESET pin is held “L”.) Also, the oscillation circuit is reset and the
main clock starts oscillating. CPU and SFRs are reset when the signal applied to the RESET pin changes from “L”
to high-level (“H”), and then the MCU executes a program beginning with the address indicated by the reset vector.
The WDC5 bit in the WDC register and the internal RAM are not reset by hardware reset 1. When an “L” signal is
applied to the RESET pin while writing data to the internal RAM, the value written to the internal RAM becomes
undefined.
Figure 5.1 shows an example of the reset circuit. Figure 5.2 shows a reset sequence. Table 5.1 lists pin states while
the RESET pin is held “L”.
5.1.1 Reset at a Stable Supply Voltage
(1) Apply an “L” signal to the RESET pin.
(2) Input 20 clock cycles or more into the XIN pin.
(3) Apply an “H” signal to the RESET pin.
5.1.2 Power-on Reset
(1) Apply an “L” signal to the RESET pin.
(2) Increase the supply voltage until it meets the recommended operating condition.
(3) Wait for td(P-R) (internal power supply stabilization time) or more to allow the internal power supply to
stabilize.
(4) Inputs 20 clock cycles or more into the XIN pin.
(5) Apply an “H” signal to the RESET pin.
VCC1
Recommended
operating volatage
VCC1
0V
RESET
RESET
0V
0.2VCC1 or below
0.2VCC1 or below
Input td(P-R) + 20 clock cycles or more
to the XIN pin
NOTE:
1. If operating at VCC1 > VCC2, VCC2 voltage must be lower than VCC1 voltage when powering up and down.
Figure 5.1 Example of Reset Circuit
Rev.1.00 Jul 15, 2007 Page 33 of 352
REJ09B0385-0100