M16C1N Datasheet, PDF (216/238 Pages) Renesas Technology Corp – RENESAS 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/10 SERIES

M16C/1N Group
20. Precautionary Notes in Using the Device
20. Precautionary Notes in Using the Device
20.1 Clock
20.1.1 External Clock
Do not stop the external clock when it is connected to the XIN pin and the main clock is selected as the
CPU clock.
20.1.2 Power Control
____________
1. When exiting stop mode by hardware reset, set RESET pin to "L" for at least 200 µs or longer.
2. Insert more than four NOP instructions after an WAIT instruction or a instruction to set the CM10 bit
of the CM1 register to "1". When shifting to wait mode or stop mode, an instruction queue reads
ahead to the next instruction to halt a program by an WAIT instruction and an instruction to set the
CM10 bit to "1" (all clocks stopped). The next instruction may be executed before entering wait
mode or stop mode, depending on a combination of instruction and an execution timing.
3. In the main clock oscillation or low power dissipation mode, set the CM02 bit of the CM0 register to
"0" (do not stop peripheral function clock in wait mode).
4. Wait until the td(M-L) elapses or main clock oscillation stabilization time, whichever is longer, be-
fore switching the clock source for CPU clock to the main clock.
Similarly, wait until the sub clock oscillates stably before switching the clock source for CPU clock
to the sub clock.
5. Suggestions to reduce power consumption
• Ports
The processor retains the state of each I/O port even when it goes to wait mode or to stop
mode. A current flows in active I/O ports. A pass current flows in input ports that high-imped-
ance state. When entering wait mode or stop mode, set non-used ports to input and stabilize
the potential.
• A/D converter
When A/D conversion is not performed, set the VCUT bit of the ADCON1 register to "0" (VREF
not connection). When A/D conversion is performed, start the A/D conversion at least 1 µs or
longer after setting the VCUT bit to "1" (VREF connection).
• D/A converter
When not performing D/A conversion, set the DAE bit of the DACON register to "0" (input
inhibited) and DA register to "0016".
• Switching the oscillation-driving capacity
Set the driving capacity to "LOW" when oscillation is stable.
• External clock
When using an external clock input for the CPU clock, set the CM05 bit of the CM0 register to
"1" (stop). Setting the CM05 bit to "1" disables the XOUT pin from functioning, which helps to
reduce the amount of current drawn in the chip. (When using an external clock input, note that
the clock remains fed into the chip regardless of how the CM05 bit is set.)
Rev.1.00 Oct 20, 2004 page 204 of 222
REJ090007-0100Z