Hardware Reset; When Power Supply Is Stable; Power On - Renesas R8C Series User Manual

R8C/1A Group, R8C/1B Group
6.1

Hardware Reset

A reset is applied using the RESET pin. When an "L" signal is applied to the RESET pin while the supply voltage
meets the recommended operating conditions, pins, CPU, and SFRs are reset (refer to Table 6.2 Pin Functions
while RESET Pin Level is "L"). When the input level applied to the RESET pin changes from "L" to "H", a
program is executed beginning with the address indicated by the reset vector. After reset, the low-speed on-chip
oscillator clock divided by 8 is automatically selected as the CPU clock.
Refer to 4. Special Function Registers (SFRs) for the state of the SFRs after reset.
The internal RAM is not reset. If the RESET pin is pulled "L" while writing to the internal RAM is in progress, the
contents of internal RAM will be undefined.
Figure 6.4 shows an Example of Hardware Reset Circuit and Operation and Figure 6.5 shows an Example of
Hardware Reset Circuit (Usage Example of External Supply Voltage Detection Circuit) and Operation.
6.1.1

When Power Supply is Stable

(1) Apply "L" to the RESET pin.
(2) Wait for 500 µs (1/fRING-S × 20).
(3) Apply "H" to the RESET pin.
6.1.2

Power On

(1) Apply "L" to the RESET pin.
(2) Let the supply voltage increase until it meets the recommended operating condition.
(3) Wait for td(P-R) or more to allow the internal power supply to stabilize (refer to 19. Electrical
Characteristics).
(4) Wait for 500 µs (1/fRING-S × 20).
(5) Apply "H" to the RESET pin.
Rev.1.30 Dec 08, 2006
REJ09B0252-0130
Page 40 of 315
6. Resets