HT46R064D/065D/066D
Enhanced A/D Type 8-Bit OTP MCU with LED Driver
It should be noted that, no matter what condition the LXTLPbit is set to, the LXToscillator will always
function normally, the only difference is that it will take more time to start up if in the Low-power
mode.
Internal Low Speed Oscillator - LIRC
The LIRC is a fully self-contained free running on-chip RC oscillator with a typical frequency of
13kHz at 5V requiring no external components. When the device enters the Sleep Mode, the system
clock will stop running but the WDT oscillator continues to free-run and to keep the watchdog active.
However, to preserve power in certain applications the LIRC can be disabled via a configuration
option.
Operating Modes
By using the LXT low frequency oscillator in combination with a high frequency oscillator, the system
can be selected to operate in a number of different modes. These Modes are Normal, Slow and Sleep.
Mode Types and Selection
The higher frequency oscillators provide higher performance but carry with it the disadvantage of
higher power requirements, while the opposite is of course true for the lower frequency oscillators.
With the capability of dynamically switching between fast and slow oscillators, the device has the
flexibility to optimise the performance/power ratio, a feature especially important in power sensitive
portable applications.
For these devices, if the LXT oscillator is used then the internal RC oscillator, HIRC, must be used as
the high frequency oscillator. If the HXT or the ERC oscillator is chosen as the high frequency system
clock then the LXT oscillator cannot be used for sharing the same pins. The CLKMOD bit in the
CTRL0 register can be used to switch the system clock from the high speed HIRC oscillator to the low
speed LXT oscillator. When the HALT instruction is executed and the device enters the Sleep Mode
the LXT oscillator will always continue to run. For these devices the LXT crystal is connected to the
OSC1/OSC2 pins and LXT will always run (the LXTEN bit is not used).
Note that CLKMOD is only valid in HIRC+LXT oscillator configuration.
System Clock Configurations
Rev. 1.00
30
January 12, 2011
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
