HMCS~C--------------------------------------------------------------
Do
GND
"¥-"
_-o--o-J
Fig. 17 Recommendable Layout
of
Crystal
and
Ceramic Filter
•
LOW
POWER
DISSIPATION
MODE
The
MCU
provides two low power dissipation modes, that
is,
a Standby mode and a Stop mode. Table
21
shows the function
of
the low power dissipation mode, and Fig.
18
shows the
diagram
of
the mode transition.
Table
21
Low Power Dissipation Mode Function
Condition
Low
Power
Instruction
Input!
Timer!
Recovering
Dissipation Mode
Oscillator
Instruction
Register.
Interrupt
RAM
Output
Counter.
method
circuit
execution
Flag
function
pin
Serial
Interfece
Standby mode
SBY
Active
Stop
Retained Active
'31
RESET
Input,
instruction
Retained
Retained
Active
Interrupt
request
Stop
mode
STOP
Stop Stop
RESET'I)
Stop
Retained
High'21
Stop
RESET
Input
instruction
impedance
·1)
As the
MCU
recovers
from
STOP mode
by
RESET
input,
the contents
of
the flags and registers I!re initialized according
to
Table
19.
·2)
A high voltage
pin
with
a
pull-down
MOS
option
is
pulled
down
to
the Vdisp power supply
by
the pull-down MOS.
As
the
MOS
is
ON. a
pull-
down MOS current
flows
when a voltage difference between the
pin
and the Vdisp voltage exists. This
is
the additional current
to
the current dis-
sipation
in
Stop Mode
(I,top)'
·3)
As.
I/O
circuit
is
active. a
I/O
current possibly flows according the state
of
I/O
pin.
This
is
the
additional current
to
the current dissipation in
Standby Mode
(lSBY1,
ISBY2)'
Fig. 18 MCU Operation Mode Transition
• Standby Mode
The
SBY
instruction puts the
MCU
into the Standby mode.
In the Standby mode, the oscillator circuit
is
active and timer/
248
counter and serial interface continue working. On the other
hand, the
CPU
stops since the clock related to the instruction
execution stops. Registers,
RAM
and Input/Output pins retain
the state they had just before going into the
Standby mode.
The
Standby mode
is
canceled by the
MCU
reset or interrupt
request.
When
canceled by the interrupt request, the
MCU
becomes
an
active mode and executes the instruction next to
the
SBY
instruction. At this time,
if
the Interrupt Enable Flag
is
"I",
the interrupt
is
executed.
If
the Interrupt Enable Flag
is
"0",
the interrupt request
is
held
on
and the normal instruc-
tion execution continues.
Fig.
19
shows the flowchart
of
the Standby
Mode
.
•
Stop
Mode
The
STOP
instruction brings the
MCU
into the Stop mode.
In this mode the oscillator circuit and every function
of
the
MCU
stop.
The
Stop mode
is
canceled by the
MCU
reset. At this time,
as
shown
in
Fig. 20, apply the RESET input for more than tRe
to get enough oscillator stabilization time. (Refer to the
"AC
CHARACTERISTICS".)
After the Stop mode
is
canceled,
RAM
retains the state it had just before going into the Stop
mode. The other hand, Accumulator, B Register, W Register,
X/SPX
Registers, Y/SPY Registers, Carry and Serial Data
Register don't retain the contents.
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