EM77950
BB Controller
17.2 Green Mode
The “GREEN” bit of WDTC [7] register is the only control bit used for mode switching
between normal mode and green mode. Its initial value is “0”, normal mode. When
“GREEN” bit is written with a 1, the MCU will switch to green mode from normal mode.
In contrast, the MCU will go back to normal mode when the “GREEN” bit is written from
1 to 0. During green mode, the main oscillator and PLL will be turned off. The MCU
and all the peripherals are driven by the internal RC oscillator - IRC.
Once BB peripheral is functional and then switched into green mode, the clock source
of all other peripherals, except PLL, will be provided by IRC. PLL will keep running as
BB circuit’s clock source.
17.3 Sleep Mode
The execution of “SLEP” instruction will turn the whole chip into Sleep mode. The main
clock will be shut down. The IRC oscillator is halted also if the watchdog function is
disabled. All registers, memory and I/O port remain in their previous states during
sleep mode. The overflow of the watchdog timer driven by IRC will generate a reset to
resume normal operation. Key Wake up (KWU) interrupt and /RESET pin are other
methods to exit sleep mode. It is essential to wait for stable Oscillation start-up time
before normal operation. The stabilizing time is SST.
Product Specification (V1.0) 10.09.2007
(This specification is subject to change without further notice)
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ELAN [ ELAN MICROELECTRONICS CORP ]
