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297
User’s Manual U15017EJ2V0UD
CHAPTER 17 STANDBY FUNCTION
17.1 Configuration and Function
The
μ
PD784975A 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 operating 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 17-1.
Figure 17-1. Standby Mode Transition Diagram
Notes 1.
When INTP0 to INTP2 are not masked
2.
Unmasked interrupt request only
Remark
The watchdog timer must not be used to release the standby mode (STOP, HALT, or IDLE mode).
Wait for
oscillation
stabilization
Normal
operation
(Main system
clock operation)
Macro
service
Macro service request
1st service request
End of macro service
Interrupt request
Note2
Macosevce
reques
1s sevcereques
STOP setting
INTP0 to INTP2 input
Note 1
RESET input
IDLE settng
RESET input
RESET input
INTP0toINTP2inpu
Noe1
Masked interrupt
request
(Standby)
INTP0 to INTP2 nput
HALT settng
Masked interrupt
request
Masked
interrupt
request
HALT
(Standby)
IDLE
STOP
(Standby)
Elbm