Chapter 13 Standby Function; Standby Function And Configuration; Standby Function - NEC 78K0S/KA1+ Preliminary User's Manual

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13.1 Standby Function and Configuration

13.1.1 Standby function

Operation Mode
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Reset
STOP
HALT
Notes 1.
2.
3.
Caution The LSRSTOP setting is valid only when "Can be stopped by software" is set for the low-speed
Ring-OSC oscillator by the option byte.
Remark LSRSTOP: Bit 0 of the low-speed Ring-OSC mode register (LSRCM)
The standby function is designed to reduce the operating current of the system. The following two modes are
available.
(1) HALT mode
HALT instruction execution sets the HALT mode. In the HALT mode, the CPU operation clock is stopped.
Oscillation of the system clock oscillator continues. If the low-speed Ring-OSC oscillator is operating before
the HALT mode is set, oscillation of the clock of the low-speed Ring-OSC oscillator continues (refer to Table
13-1. Oscillation of the low-speed Ring-OSC clock (whether it cannot be stopped or can be stopped by
software) is set by the option byte). In this mode, the operating current is not decreased as much as in the
STOP mode, but the HALT mode is effective for restarting operation immediately upon interrupt request
generation and carrying out intermittent operations.
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CHAPTER 13 STANDBY FUNCTION

Table 13-1. Relationship Between Operation Clocks in Each Operation Status
Status Low-Speed Ring-OSC Oscillator
Note 1
Stopped
Oscillating Oscillating
When "Cannot be stopped" is selected for low-speed Ring-OSC by the option byte.
When it is selected that the low-speed Ring-OSC oscillator "can be stopped by software", oscillation of
the low-speed Ring-OSC oscillator can be stopped by LSRSTOP.
If the operating clock of the watchdog timer is the low-speed Ring-OSC clock, the watchdog timer is
stopped.
Preliminary User's Manual U16898EJ1V0UD
Note 2
LSRSTOP = 0 LSRSTOP = 1
Note 3
Stopped
System Clock Clock Supplied to
Peripheral
Hardware
Stopped Stopped
Oscillating Oscillating