E202075_HD404889 Datasheet, PDF (60/202 Pages) Renesas Technology Corp – Low-Voltage AS Microcomputers with On-Chip LCD Circuit

HD404889/HD404899/HD404878/HD404868 Series
Direct transition from subactive to active mode:
A direct transition can be made from subactive mode to active mode by controlling the direct transfer on
flag (DTON: $020,3) and low speed on flag (LSON: $020,0). The procedure is shown below.
(a) Set LSON = 0 and DTON = 1 in subactive mode.
(b) Execute a STOP or SBY instruction.
(c) After the lapse of the MCU internal processing time and the oscillation settling time, the MCU
automatically switches from subactive mode to active mode (figure 18).
Notes: 1. The DTON flag ($020,3) can be set in only subactive mode. It is always in the reset state in
active mode.
2. The condition for transition time T_D from the subactive mode to active mode is as follows:
t_RC < T_D < T + t_RC.
Subactive mode
(Set LSON =0, DTON =1)
STOP/SBY
instruction execution
MCU internal
processing time
Oscillation
stabilization time
Active mode
Interrupt strobe
Direct transition
completion timing
T
tRC
T_D
T: Interrupt frame period
tRC: Oscillation settling time
T_D: Direct transition time
Figure 18 Direct Transition Timing
MCU operation sequence:
The MCU operates in accordance with the flowchart shown in figure 19. RESET input is asynchronous
input, and the MCU immediately enters the reset state upon RESET input, regardless of its current state.
In the low-power mode operation sequence, if a STOP/SBY instruction is executed while the IE flag is
cleared and the interrupt flag is set, releasing the relevant interrupt mask, the STOP/SBY instruction is
canceled (regarded as NOP) and the next instruction is executed. Therefore, when executing a STOP/SBY
instruction, all interrupt flags must be cleared, or interrupts masked, beforehand.
58