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(5) Before the count source for BCLK can be changed from X
count source is going to be switched must be oscillating stably. Allow a wait time in software for the oscilla-
tion to stabilize before switching over the clock.
(6) Suggestions to reduce power consumption
(a) Ports
The processor retains the state of each programmable 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 float. When
entering wait mode or stop mode, set non-used ports to input and stabilize the potential.
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(b) Memory expansion mode and microprocessor mode
When the MCU enters wait mode while operating in memory expansion mode or microprocessor
mode, a pin functioning as part of the address or data bus retains it's state on the bus before wait
mode is entered. Shift to single-chip mode and output an arbitrary value in order to reduce current
consumption. By shifting to single-chip mode, a pin which was functioning as part of the bus be-
comes a general-purpose port and can output an arbitrary value. Set the port registers and direction
registers after shifting to single-chip mode (this implies that any control pins (CS, WR, RD, etc.. )
being used for access of an external device be changed as well).
The same applies to stop mode.
(c) A/D converter
A current always flows in the V
tion bit to "0" so that no current flows into the V
(d) Stopping peripheral functions
In wait mode, stop non-used peripheral functions using the WAIT peripheral function clock stop bit.
However, peripheral function clock f
tribute to the power saving. When the MCU running in low-speed or low power dissipation mode, do
not enter WAIT mode with this bit set to "1".
(e) External clock
When using an external clock input for the CPU clock, set the main clock stop bit to "1". Setting the
main clock stop bit to "1" causes the X
(when using an external clock input, the clock signal is input regardless of the content of the main
clock stop bit).
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
pin. When entering wait mode or stop mode, set the Vref connec-
REF
C32
OUT
page 283 of 354
to X
or vice versa, the clock to which the
IN
CIN
pin.
REF
does not stop so that the peripherals using f
pin not to operate and the power consumption goes down
2. Power Control
_____
______
_____
do not con-
C32
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