BS85B12-3 HOLTEK [Holtek Semiconductor Inc], BS85B12-3 Datasheet - Page 44

• Manufacturer Part Number: BS85B12-3
• Description: Touch Key Flash Type 8-Bit MCU with LCD/LED Driver
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

Rev. 1.00
NORMAL Mode to SLOW Mode Switching
SLOW Mode to NORMAL Mode Switching
Entering the SLEEP Mode
When running in the NORMAL Mode, which uses the high speed system oscillator, and therefore
consumes more power, the system clock can switch to run in the SLOW Mode by set the HLCLK bit to
speed system oscillator which will consume less power. Users may decide to do this for certain
operations which do not require high performance and can subsequently reduce power consumption.
The SLOW Mode clock is sourced from the LIRC oscillator.
In SLOW Mode the system uses the LIRC low speed system oscillator. To switch back to the
NORMAL Mode, where the high speed system oscillator is used, the HLCLK bit should be set to 1
or HLCLK bit is 0 , but CKS2~CKS0 is set to 010 , 011 , 100 , 101 , 110 or 111 . As a
certain amount of time will be required for the high frequency clock to stabilise, the status of the HTO
bit is checked. The amount of time required for high speed system oscillator stabilization depends
upon which high speed system oscillator type is used.
There is only one way for the device to enter the SLEEP Mode and that is to execute the HALT
instruction in the application program with the IDLEN bit in SMOD register equal to 0 . When this
instruction is executed under the conditions described above, the following will occur:
0 and set the CKS2~CKS0 bits to 000 or 001 in the SMOD register. This will then use the low
The system clock will be stopped and the application program will stop at the HALT instruction,
but the f
The Data Memory contents and registers will maintain their present condition.
The WDT will be cleared and resume counting.
The I/O ports will maintain their present conditions.
In the status register, the Power Down flag, PDF, will be set and the Watchdog time-out flag, TO,
will be cleared.
LIRC
Touch Key Flash MCU with LCD/LED Driver
clock will be on.
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BS85B12-3/BS85C20-3
February 1, 2011