Datasheet

Table Of Contents
Section 22 Power-Down Modes
Page 690 of 846 REJ09B0140-0900 Rev. 9.00
Sep 16, 2010
H8S/2215 Group
22.4 Software Standby Mode
22.4.1 Transition to Software Standby Mode
A transition is made to software standby mode when the SLEEP instruction is executed when the
SSBY bit in SBYCR is 1. In this mode, the CPU, on-chip supporting modules, and oscillator all
stop. However, the contents of the CPU’s internal registers, RAM data, and the states of on-chip
supporting modules other than the A/D converter, and the states of I/O ports, are retained. In this
mode the oscillator stops, and therefore power dissipation is significantly reduced.
22.4.2 Clearing Software Standby Mode
Software standby mode is cleared by an external interrupt (NMI pin, IRQ7 pin, or IRQ0 to IRQ5
pins), USB suspend/resume interrupt (IRQ6 signal), or by means of the RES pin, MRES pin, or
STBY pin.
Clearing with an interrupt
When an NMI or IRQ0 to IRQ7 interrupt request signal is input, clock oscillation starts, and
after the elapse of the time set in bits STS2 to STS0 in SBYCR, stable clocks are supplied to
the entire chip, software standby mode is cleared, and interrupt exception handling is started.
When clearing software standby mode with an IRQ0 to IRQ7 interrupt, set the corresponding
enable bit to 1 and ensure that no interrupt with a higher priority than interrupts IRQ0 to IRQ5
is generated. Software standby mode cannot be cleared if the interrupt has been masked on the
CPU side or has been designated as a DTC activation source.
Clearing with the RES or MRES pin
When the RES or MRES pin is driven low, clock oscillation is started. At the same time as
clock oscillation starts, clocks are supplied to the entire chip. Note that the RES or MRES pin
must be held low until clock oscillation stabilizes. When the RES or MRES pin goes high, the
CPU begins reset exception handling.
Clearing with the STBY pin
When the STBY pin is driven low, a transition is made to hardware standby mode.