UPD784938 Datasheet, PDF (637/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 25 STANDBY FUNCTION
25.1 Configuration and Function
The µPD784938 has a standby function that enables the system power consumption to be reduced. The standby function
includes three modes as follows:
• HALT mode........ In this mode the CPU operating clock is stopped. Intermittent operation in combination with the
normal operation mode enables the total system power consumption to be reduced.
• IDLE mode......... In this mode the oscillator continues operating while the entire remainder of the system is stopped.
Normal program operation can be restored at a low power consumption close to that of the STOP
mode and in a time equal to that of the HALT mode.
• STOP mode........In this mode the oscillator is stopped and the entire system is stopped.
Ultra-low power consumption can be achieved, consisting of leakage current only.
These modes are set by software. The standby mode (STOP/IDLE/HALT mode) transition diagram is shown in Figure
25-1, and the standby function block diagram in Figure 25-2.
Figure 25-1. Standby Mode Transition Diagram
End ^{of oscillation stabilization time}
Wait of
oscillation
stabilization
STROEPSsEeTttiinngput
Program
operation
Macro service request
End of 1st service
End of macro service
Macro
service
STOP
(standby)
IDLE
(standby)
Masked interrupt
request
HALT
(standby)
Notes 1. When INTW, INTP4, and INTP5 are not masked
2. Unmasked interrupt request only
3. At subclock operation
Remark Only external input is valid as NMI. The watchdog timer must not be used to release the standby mode (STOP,
IDLE, or HALT mode)
Preliminary User’s Manual U13987EJ1V0UM00
637