UPD78F1502AGK-GAK-AX Datasheet, PDF (1006/1031 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcontrollers

78K0R/Lx3
Function
Details of
Function
APPENDIX C LIST OF CAUTIONS
Cautions
(34/39)
Page
Low-
voltage
detector
Regulator
Cautions for low- In a system where the supply voltage (VDD) fluctuates for a certain period in the pp.823 _†
voltage detector vicinity of the LVI detection voltage (VLVI), the operation is as follows depending on to 825
how the low-voltage detector is used.
Operation example 1: When used as reset
The system may be repeatedly reset and released from the reset status.
The time from reset release through microcontroller operation start can be set
arbitrarily by the following action.
<Action>
After releasing the reset signal, wait for the supply voltage fluctuation period of each
system by means of a software counter that uses a timer, and then initialize the ports
(see Figure 24-11).
Operation example 2: When used as interrupt
Interrupt requests may be generated frequently.
Take the following action.
<Action>
Confirm that “supply voltage (VDD) ≥ detection voltage (VLVI)” when detecting the
falling edge of VDD, or “supply voltage (VDD) < detection voltage (VLVI)” when detecting
the rising edge of VDD, in the servicing routine of the LVI interrupt by using bit 0
(LVIF) of the low-voltage detection register (LVIM). Clear bit 1 (LVIIF) of interrupt
request flag register 0L (IF0L) to 0.
For a system with a long supply voltage fluctuation period near the LVI detection
voltage, take the above action after waiting for the supply voltage fluctuation time.
There is some delay from the time supply voltage (VDD) < LVI detection voltage (VLVI) p.825 _†
until the time LVI reset has been generated.
In the same way, there is also some delay from the time LVI detection voltage (VLVI)
≤ supply voltage (VDD) until the time LVI reset has been released (see Figure 24-12).
RMC: Regulator The RMC register can be rewritten only in the low-power consumption mode (refer to p.827 _†
mode control Table 25-1). In other words, rewrite this register during CPU operation with the
register
subsystem clock (fXT) while the high-speed system clock (fMX), the high-speed
internal oscillation clock, and the 20 MHz internal high-speed oscillation clock (fIH20)
are both stopped.
When using the setting fixed to the low consumption current mode, the RMC register p.827 _†
can be used in the following cases.
<When the high-speed internal oscillation clock (fIH = 8 MHz (TYP.) or fIH = 1 MHz
(TYP.)) is selected as the CPU clock>
fCLK ≤ 1 MHz and external oscillator (X1 clock (fX), external main system clock (fEX))
stop..
<When the X1 clock (fX) or external main system clock (fEX) is selected as the CPU
clock>
fCLK ≤ 1 MHz, fX/fEX ≤ 5 MHz and the internal high-speed oscillator stop.
<When the subsystem clock (fSUB) is selected as the CPU clock>
Both the internal high-speed oscillator and external oscillator (fX/fEX ≤ 5 MHz) stop or
either one stops.
In low-power consumption mode, use the regulator with fCLK fixed to 1 MHz when p.828 _†
executing self programming.
R01UH0004EJ0501 Rev.5.01
990
Jun 20, 2011