NEC 78K0S/KA1+ User Manual page 400

Function Details of
Function
Low- When used as
voltage reset
detector
Cautions for
low-voltage
detector
Option Oscillation
byte stabilization
time on power
application or
after reset
release
Control of
RESET pin
Selection of
system clock
source
Low-speed
internal
oscillates
Flash PG-FP4 GUI
memory software setting
value example
400
APPENDIX D LIST OF CAUTIONS
<1> must always be executed. When LVIMK = 0, an interrupt may occur
immediately after the processing in <3>.
If supply voltage (V ) ≥ detection voltage (V
DD
reset signal is not generated.
In a system where the supply voltage (V
vicinity of the LVI detection voltage (V
on how the low-voltage detector is used.
<1> When used as reset
The system may be repeatedly reset and released from the reset status.
In this case, the time from release of reset to the start of the operation of the
microcontroller can be arbitrarily set by taking action (1) below.
<2> When used as interrupt
Interrupt requests may be frequently generated. Take (b) of action (2) below.
The setting of this option is valid only when the crystal/ceramic oscillation clock is
selected as the system clock source. No wait time elapses if the high-speed
internal oscillation clock or external clock input is selected as the system clock
source.
Because the option byte is referenced after reset release, if a low level is input to
the RESET pin before the option byte is referenced, then the reset state is not
released.
Also, when setting 0 to RMCE, connect the pull-up resistor.
Because the X1 and X2 pins are also used as the P121 and P122 pins, the
conditions under which the X1 and X2 pins can be used differ depending on the
selected system clock source.
(1) Crystal/ceramic oscillation clock is selected
The X1 and X2 pins cannot be used as I/O port pins because they are used as
clock input pins.
(2) External clock input is selected
Because the X1 pin is used as an external clock input pin, P121 cannot be used
as an I/O port pin.
(3) High-speed internal oscillation clock is selected
P121 and P122 can be used as I/O port pins.
If it is selected that low-speed internal oscillator cannot be stopped, the count
clock to the watchdog timer (WDT) is fixed to low-speed internal oscillation clock.
If it is selected that low-speed internal oscillator can be stopped by software,
supply of the count clock to WDT is stopped in the HALT/STOP mode, regardless
of the setting of bit 0 (LSRSTOP) of the low-speed internal oscillation mode
register (LSRCM). Similarly, clock supply is also stopped when a clock other than
the low-speed internal oscillation clock is selected as a count clock to WDT.
While the low-speed internal oscillator is operating (LSRSTOP = 0), the clock can
be supplied to the 8-bit timer H1 even in the STOP mode.
The above values are recommended values. Depending on the usage
environment these values may change, so set them after having performed
sufficient evaluations.
User's Manual U16898EJ3V0UD
Cautions
) when LVIM is set to 1, an internal
LVI
) fluctuates for a certain period in the
DD
), the operation is as follows depending
LVI
(14/17)
Page
p. 252
p. 252
p. 256
p. 260
p. 260
p. 260
p. 261
p. 261
p. 269