C165UTAH Datasheet, PDF (451/539 Pages) Infineon Technologies AG – EMBEDDED C166 WITH USART IOM-2 AND HDLC SUPPORT

C165UTAH
Power Reduction Modes
20
Power Reduction Modes
Two different power reduction modes with different levels of power reduction have been
implemented in the C165UTAH, which may be entered under software control.
In Idle mode the CPU is stopped, while the peripherals continue their operation. Idle
mode can be terminated by any reset or interrupt request.
In Power Down mode both the CPU and the peripherals are stopped. Power Down
mode can only be terminated by a hardware reset.
Note: All external bus actions are completed before Idle or Power Down mode is
entered. However, Idle or Power Down mode is not entered if READY is enabled,
but has not been activated (driven low) during the last bus access.
20.1
Idle Mode
The power consumption of the C165UTAH microcontroller can be decreased by entering
Idle mode. In this mode all peripherals, including the watchdog timer, continue to
operate normally, only the CPU operation is halted.
Idle mode is entered after the IDLE instruction has been executed and the instruction
before the IDLE instruction has been completed. To prevent unintentional entry into Idle
mode, the IDLE instruction has been implemented as a protected 32-bit instruction.
Idle mode is terminated by interrupt requests from any enabled interrupt source whose
individual Interrupt Enable flag was set before the Idle mode was entered, regardless of
bit IEN.
For a request selected for CPU interrupt service the associated interrupt service routine
is entered if the priority level of the requesting source is higher than the current CPU
priority and the interrupt system is globally enabled. After the RETI (Return from
Interrupt) instruction of the interrupt service routine is executed the CPU continues
executing the program with the instruction following the IDLE instruction. Otherwise, if
the interrupt request cannot be serviced because of a too low priority or a globally
disabled interrupt system the CPU immediately resumes normal program execution with
the instruction following the IDLE instruction.
For a request which was programmed for PEC service a PEC data transfer is performed
if the priority level of this request is higher than the current CPU priority and the interrupt
system is globally enabled. After the PEC data transfer has been completed the CPU
remains in Idle mode. Otherwise, if the PEC request cannot be serviced because of a
too low priority or a globally disabled interrupt system the CPU does not remain in Idle
mode but continues program execution with the instruction following the IDLE
instruction.
Data Sheet
451
2001-02-23