R8C13 datasheet(29/224 Pages) RENESAS

29 / 224 page

Rev.1.20

Jan 27, 2006

page 18 of 205

REJ09B0111-0120

R8C/13 Group

5.1.3 Power-on Reset Function

The power-on reset is the function which can reset the microcomputer without the external reset

____________

circuit. The RESET pin should be connected to the VCC pin via about 5 k

Ω pull-up resistance using

the power-on reset function, the function turns to active and the microcomputer has its pins, CPU,

____________

and SFR initialized. When a capacitor is connected to the RESET pin, always keep the voltage to the

____________

RESET pin 0.8 VCC or more.

When the input voltage at the VCC pin reaches to the Vdet level, count operation of the low-speed on-

chip oscillator clock starts. When the operation counts the low-speed on-chip oscillator clock for 32

times, the internal reset is released. Then the program is executed starting from the address indi-

cated by the reset vector. The initialized pins and registers and the status thereof are the same as in

hardware reset 1 excluding the following bits.

• The D40 bit in the D4INT register turns to “1” automatically (voltage detection interrupt enabled)

• The D46 bit in the D4INT register turns to “1” automatically (hardware reset 2 when going through

Vdet)

Additionally, the hardware reset 2 turns to active after the power-on reset. This is because the VC27

bit in the VCR2 register is set to “1” (voltage detection circuit enabled) after the power-on reset same

as the hardware reset 1, so that hardware reset 2 active conditions are all satisfied including above

D40 and D46 bit conditions.

Figure 5.5 shows the power-on reset circuit. Figure 5.6 shows the power-on reset operation.

Figure 5.5 Power-on Reset Circuit

Internal reset signal

RESET

VCC

≥ Vdet detection

5-bit

counter

fRING-S

Trigger

5.1 Hardware Reset

R8C13 датащи(PDF) 29 Page - Renesas Technology Corp