Infineon XC800 Series, Руководство пользователя

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AP08056
Power Saving Features
Stopping the CPU Clock (Idle Mode)
Application Note 6 V1.0, 2006-12
The device in idle mode can be exited to active mode on the occurrence of any of the
two conditions:
1. Hardware reset. The device is put into the hardware reset state.
2. An interrupt has occurred from an enabled interrupt source. The device will service
the interrupt routine and continue its operation from the next instruction after the
instruction that sets the PCON.IDLE bit to 1.
2.2 Ineffective Idle Mode
Idle mode may not necessarily be useful in reducing power consumption. If interrupt
events keep occurring, the device will not be able to stay in idle mode and therefore is
unable to reduce power consumption. In the below example, the peripherals of the
devices were configured to operate as follows:
•
Timers 0/1/2/21 in autoreload mode to overflow after 0xFFFF counts
• ADC to perform 10-bit parallel conversion in autoscan mode
• CCU to generate PWM output upon every period match
• UART0 and UART1 to transmit data at 19.2 kBaud upon each UART interrupt
• SSC to transmit at 3 MBaud upon each SSC interrupt
• CORDIC to start computation in circular rotation mode upon each CORDIC interrupt
• MDU to perform unsigned multiplication upon each MDU interrupt
• MCAN to start 8 bytes transmission in loopback mode upon each MCAN interrupt
Note: UART1, CORDIC, MDU and MCAN were configured for XC886/888 only.
The current consumption of the devices is as follow:
Looking at the amount of actives, the devices will be too busy serving the interrupt
routines that they may never be able to stay in idle mode (i.e. turn off the CPU). It can
be observed from
Table 2 that idle mode has no effect on the current consumption since
the CPU is always active.
Table 2 Current consumed by devices with peripheral activities
Product CPU Clock Active
Current (mA) Idle Current
(mA) Difference
1)
(mA)
1) Negative value indicates that Idle mode current > Active mode current.
XC866-1FR 26.80 MHz 15.88 15.89 - 0.01 mA
XC866-4FR 26.61 MHz 18.52 18.53 - 0.01 mA
XC886 24.375 MHz 25.01 25.07 -0.06 mA
XC888 24.125 MHz 24.82 24.89 - 0.07 mA