HD404019R Datasheet, PDF (37/65 Pages) Renesas Technology Corp – CMOS 4-bit single-chip microcomputers

HD404019R Series
Operating Modes
The MCU has two low-power dissipation modes, standby mode and stop mode (table 21). Figure 18 is a
mode transition diagram for these modes.
Standby Mode: Executing the SBY instruction puts the MCU into standby mode. In standby mode, the
oscillator circuit is active, and the interrupts, timer/counters, and serial interface remain working. On the
other hand, the CPU stops since the clock related to the instruction execution stops. Registers, RAM, and
I/O pins retain the states they were in just before the MCU went into standby mode.
Table 21 Low-Power Dissipation Modes
Condition
Standby Mode
Stop Mode
Instruction
SBY instruction
STOP instruction
Oscillator circuit
Active
Stopped
Instruction execution
Stopped
Stopped
Registers, flags
Retained
Reset*¹
Interrupt function
Active
Stopped
RAM
Retained
Retained
Input/output pins
Retained*²
High impedance
Timer/counters, serial interface Active
Stopped
Cancellation method
RESET input, interrupt request RESET input
Notes: 1. The MCU recovers from the stop mode by RESET input. Refer to table 19 for the contents of
flags and registers.
2. When I/O circuits are active, an I/O current may flow in the standby mode, depending on the
state of the I/O pins. This is an additional current added to the standby mode current dissipation.
SBY
instruction
Active
mode
STOP
instruction
Standby
mode
Interrupt
request
RESET = 1 RESET = 0
Stop
mode
RESET = 1
RESET = 1
Reset
Figure 18 MCU Operating Mode Transition
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