Power-On Reset Function - Renesas M16C FAMILY Hardware Manual

Under development
Preliminary specification
Specifications in this manual are tentative and subject to change.
R8C/11 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 V
the power-on reset function, the function turns to active.
When the input voltage at the V
ring oscillator clock starts. When the operation counts the low-speed ring oscillator clock for 32 times,
the microcomputer has its pins, CPU, and SFR initialized. Then the program is executed starting
from the address indicated by the reset vector. The initialized pins and registers and the status
thereof are the same as in hardware reset 1.
• 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.
RESET
f
RING-S
≥
V Vdet detection
CC
Figure 5.5 Power-on Reset Circuit
R E S E T V c c
a b o u t
5 kΩ
I n t e r n a l r e s e t s i g n a l
Figure 5.6 Power-on Reset Operation
Rev.0.91 2003 Sep 08
pin reaches to the Vdet level, count operation of the low-speed
CC
5 bit
counter
Trigger
V
C C
0.5 V
0 V
1 m s o r m o r e
page 18 of 184
pin via about 5 kΩ pull-up resistance using
CC
Q
S
R
2 . 7 V
Less than100 µs
5.1 Hardware Reset
Internal reset signal
V d e t
1
f x 3 2
R I N G - S