Rev. 3.0, 10/02, page 618 of 686
Oscillator
NMI
NMIEG
SSBY
NMI exception
handling
NMIEG = 1
SSBY = 1
Oscillation
stabilization
time t
OSC2
Software standby mode
(power-down mode)
NMI exception
handling
SLEEP instruction
Figure 22.3 Software Standby Mode Application Example
22.5
Hardware Standby Mode
22.5.1
Transition to Hardware Standby Mode
When the
STBY
pin is driven low, a transition is made to hardware standby mode from any mode.
In hardware standby mode, all functions enter the reset state and stop operation, resulting in a
significant reduction in power dissipation. As long as the prescribed voltage is supplied, on-chip
RAM data is retained. I/O ports are set to the high-impedance state.
In order to retain on-chip RAM data, the RAME bit in SYSCR should be cleared to 0 before
driving the
STBY
pin low.
Do not change the state of the mode pins (MD2 to MD0) while the this LSI is in hardware standby
mode.
22.5.2
Clearing Hardware Standby Mode
Hardware standby mode is cleared by means of the
STBY
pin and the
RES
pin. When the
STBY
pin is driven high while the
RES
pin is low, the reset state is set and clock oscillation is started.
Ensure that the
RES
pin is held low until the clock oscillator stabilizes (at least t
osc1
—the
oscillation stabilization time—when using a crystal oscillator). When the
RES
pin is subsequently
Summary of Contents for H8S/2215 Series
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