Hitachi AP1 Data Book page 325

--------------------------------------------------------------------------HMCS404AC
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
Interface
Standby mode
SBY
'J}
RESET Input,
instruction
Active Stop Retained Active Retained
Retained Active
Interrupt request
Stop mode
STOP
Stop Stop
RESET·
,1
Stop Retained
High· 21
Stop
RESET Input
instruction impedance
*1 )
*2)
As the MCU recovers from STOP mode by RESET input, the contents of the flags and registers are initialized according to Table 19.
*3)
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 (lstop).
As a 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 dissipution in
Standby Mode (lSBY1, ISBY2)'
Fig. 18 MCU Operation Mode Transition
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 "1 ", 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 MeU into the Stop mode.
In this mode the oscillator circuit and every function of the
MCU stop.
• Standby Mode
The Stop mode is canceled by the MCU reset. At this time,
as shown in Fig. 20, apply the RESET input for more than
tRC
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.
The SBY instruction puts the MCU into the Standby mode.
In the Standby mode, the oscillator circuit is active and timer/
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