M16C62_M Datasheet, PDF (533/615 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/60 SERIES

Controlling Power Applications
Mitsubishi microcomputers
M16C / 62A Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
3.8 Controlling Power Using Wait Mode
Overview The following are steps for controling power using wait mode. Figure 3.8.1 shows the operation
timing, and Figures 3.8.2 to 3.8.4 show the set-up procedure.
Use the following peripheral functions:
• Timer mode of timer B
• Wait mode
A flag named “F-WIT” is used in the set-up procedure. The purpose of this flag is to decide
whether or not to clear wait mode. If F_WIT = “1” in the main program, the wait mode is entered;
if F_WIT = “0”, the wait mode is cleared.
Specifications
(1) Connect a 32.768-kHz oscillator to XCIN to serve as the timer count source. As interrupts
occur every one second, which is a count the timer reaches, the controller returns from wait
mode and count the clock using a program.
________
(2) Clear wait mode if a INT0 interrupt request occurs.
Operation (1) Switch the system clock from XIN to XCIN to get low-speed mode.
_______
(2) Stop XIN and enter wait mode. In this instance, enable the timer B2 interrupt and the INT0 interrupt.
(3) When a timer B2 interrupt request occurs (at 1-second intervals), start supplying the BCLK
from XCIN.
At this time, count the clock within the routine that handles the timer B2 interrupts and enter wait
mode again.
_______
(4) If a INT0 interrupt occurs, start supplying the BCLK from XCIN. Start the XIN oscillation within
_______
the INT0 interrupt, and switch the system clock to XIN.
XOUT
(1) Shift to low-speed mode
(2) Stop XIN
(3) Timer B2 interrupt
(4) INT0 interrupt
XCIN
Timer B2 overflow
Timer B2
interrupt processing
“H”
INT0
“L”
BCLK
High-speed
Low-speed
Low-speed
Low-speed
Figure 3.8.1. Operation timing of controling power using wait mode
High-speed
Low-speed
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