SH7137 Datasheet, PDF (1028/1160 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperH™ RISC engine Family

Section 24 Power-Down Modes
24.5.2 Canceling Software Standby Mode
Software standby mode is canceled by interrupts (NMI, IRQ) or a reset.
Canceling with Interrupt: The WDT can be used for hot starts. When an NMI or IRQ interrupt
(edge detection) is detected, the clock will be supplied to the entire LSI and software standby
mode will be canceled after the time set in the timer control/status register of the WDT has
elapsed. Interrupt exception handling is then executed.
When the priority level of an IRQ interrupt is lower than the interrupt mask level set in the status
register (SR) of the CPU, an interrupt request is not accepted preventing software standby mode
from being canceled.
When falling-edge detection is selected for the NMI pin, drive the NMI pin high before making a
transition to software standby mode. When rising-edge detection is selected for the NMI pin, drive
the NMI pin low before making a transition to software standby mode.
Similarly, when falling-edge detection is selected for the IRQ pin, drive the IRQ pin high before
making a transition to software standby mode. When rising-edge detection is selected for the IRQ
pin, drive the IRQ pin low before making a transition to software standby mode.
Canceling with Power-on Reset: Software standby mode is canceled by a power-on reset with
the RES pin. Keep the RES pin low until the clock oscillation settles.
Rev. 2.00 Sep. 10, 2008 Page 1002 of 1130
REJ09B0402-0200