HT67F86A Internal RTC Application Guidelines
AN0448E V1.00
1/7
January 16, 2017
HT67F86A Internal RTC Application Guidelines
D/N: AN0448E
Introduction
One special feature of the Holtek 8-bit Flash MCU, the HT67F86A, is that it includes an
ultra-low power consumption RTC oscillator and an LCD driver. To meet the demands for
low power consumption applications, the device’s internal RTC has a standby power
consumption of lower than 1µA at an operating voltage of 3V. The integrated LCD driver
can drive dot matrix LCD display applications of up to 1024 pixels, which can be used with
various display configurations and font settings. With the increasing trends of mobile
device applications such as cellphones and tablets, in addition to being utilised in
industrial control and consumer products, the ultra-low standby power consumption
performance is also an especially important consideration in battery-powered applications.
The MCU’s internal RTC oscillator forms an excellent solution for applications which
require a real time clock function as it reduces the need for an external timing IC with the
resulting reductions in cost and design simplification. This application note will introduce
the Holtek MCU internal RTC oscillator characteristics and application guidelines.
Functional Description
Oscillators
The HT67F86A provides 3 frequency oscillation sources, namely the HXT, HITC and LXT
oscillators. Users can select their desired system frequency, f
SYS,
using their application
program. The LXT provides an f
L
frequency of 32768Hz for various MCU clocks, but more
commonly for applications requiring an RTC real-time clock. Additionally, the MCU can
enter the IDLE2 or SLEEP power saving modes also using the application program to
implement different standby power consumption power down modes. The related
registers are listed in the following table, refer to the Oscillators section in the datasheet
for more detailed information.
Register
Name
Bit
7
6
5
4
3
2
1
0
SCC CKS2
CKS1
CKS0
—
FHS —
FHIDEN
FSIDEN
HIRCC — — — —
HIRC1
HIRC0
HIRCF
HIRCEN
HXTC — — — — —
HXTM
HXTF
HXTEN
LXTC
— — — — — —
LXTF
LXTEN
System Operating Mode Control Registers List
