
26
μ
PD78001B(A), 78002B(A)
7.
EXTERNAL DEVICE EXPANSION FUNCTIONS
The external device expansion function is used to connect external devices to areas other than the internal ROM,
RAM and SFR.
Ports 4 to 6 are used for connection with external devices.
8.
STANDBY FUNCTIONS
There are the following two standby functions to reduce the current dissipation.
HALT mode
: The CPU operating clock is stopped. The average consumption current can be reduced by
intermittent operation in combination with the normal operating mode.
STOP mode
: The main system clock oscillation is stopped. The whole operation by the main system clock is
stopped, so that the system operates with ultra-low power consumption using only the sub-
system clock.
Fig. 8-1 Standby Functions
*
The power consumption can be reduced by stopping the main system clock. When the CPU is operating on the
subsystem clock, set the MCC to stop the main system clock. The STOP instruction cannot be used.
Caution
When the main system clock is stopped and the system is operated by the subsystem clock, the
subsystem clock should be switched again to the main system clock after the oscillation stabilization
time is secured by the program by the program.
9.
RESET FUNCTION
There are the following two reset methods.
External reset input by RESET pin.
Internal reset by watchdog timer runaway time detection.
Main System
Clock Operation
STOP Mode
(Main system clock
oscillation stopped)
HALT Mode
(Clock supply to CPU is
stopped, oscillation)
Subsystem Clock
Operation
*
HALT Mode
*
(Clock supply to CPU is
stopped, oscillation)
Interrupt
Request
Interrupt
Request
Interrupt
Request
HALT
Instruction
HALT
Instruction
STOP
Instruction
CSS=1
CSS=0