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SC140 DSP Core Reference Manual
Program Control
5.4.4 Wait Processing State
The wait processing state is a low-power consumption state entered by the execution of the WAIT
instruction. After ten core clock cycles from the issue of the WAIT instruction, the core’s global clock is
turned off. Peripherals can continue to operate, but all internal processing is halted until one of the
following actions occurs:
An enabled interrupt is issued.
A non-maskable interrupt (NMI) request is issued.
A low-level is applied to the RESET signal (RESET asserted).
The JTAG issues a debug request.
The EE0 signal (programmed as a debug request input) is asserted.
If an exit from the wait state is caused by a high level on the EE0 signal or a debug request, and the IME bit
in the EOnCE EMCR register is not set, the core enters the debug state immediately. If the IME bit is set,
the debug exception is serviced instead of entering the debug state.
Table 5-13 describes the wait process under various core conditions.
Table 5-13. Wait Processing
5.4.5 Stop Processing State
The stop processing state is the lowest power consumption mode and is entered by the execution of the
STOP instruction. After the STOP instruction has been issued, it takes ten core clock cycles to enter the
stop state and turn off the global clocks to the entire core and peripherals.
All activity in the core is halted until one of the following actions occurs:
A low level is applied to an external dedicated signal.
A low level is applied to the RESET signal (RESET asserted).
The JTAG issues a debug request.
The EE0 signal (programmed as a debug request input) is asserted.
Any of the above actions turn on the oscillator. After a clock stabilization delay, clocks to the core are
re-enabled. If the stop processing state is exited by assertion of the RESET signal, the core enters the reset
processing state.
Interrupt Priority Level (IPL)
Disable Interrupts (DI)
Wait Process
Request IPL > core IPL as determined
by the I2–I0 bits of the SR
Clear (interrupts
enabled)
Exit the wait processing state.
Jump to the Interrupt Service Routine (ISR).
Request IPL > core IPL as determined
by the I2–I0 bits of the SR
Set (interrupts disabled)
Exit the wait processing state.
Enter execution state and continue program
execution.
No jump to the ISR.
Request IPL <= core IPL as determined
by the I2–I0 bits of the SR
Clear or set
Remain in the wait processing state.
An NMI is asserted
Clear or set
Exit the wait processing state.
Jump to the ISR.