HT68F14 HOLTEK [Holtek Semiconductor Inc], HT68F14 Datasheet - Page 30

• Manufacturer Part Number: HT68F14
• Description: Enhanced I/O Flash Type MCU
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

Operating Modes and System Clocks
Rev. 1.10
NORMAL Mode
SLOW Mode
IDLE0 Mode
IDLE1 Mode
SLEEP0 Mode
SLEEP1 Mode
Operation Mode
System Clocks
System Operation Modes
Present day applications require that their microcontrollers have high performance but often still
demand that they consume as little power as possible, conflicting requirements that are especially true
in battery powered portable applications. The fast clocks required for high performance will by their
nature increase current consumption and of course vice versa, lower speed clocks reduce current
consumption. As Holtek has provided these devices with both high and low speed clock sources and
the means to switch between them dynamically, the user can optimise the operation of their
microcontroller to achieve the best performance/power ratio.
The device has many different clock sources for both the CPU and peripheral function operation. By
providing the user with a wide range of clock options using configuration options and register
programming, a clock system can be configured to obtain maximum application performance.
The main system clock can come from a high frequency f
using the HLCLK bit and CKS2~CKS0 bits in the SMOD register. The high speed system clock can be
sourced from either a HXT, ERC or HIRC oscillator, selected via a configuration option. The low
speed system clock source can be sourced from internal clock f
by the LIRC oscillator. The other choice, which is a divided version of the high speed system oscillator
has a range of f
speed oscillation will stop to conserve the power. Thus there is no f
There are two additional internal clocks for the peripheral circuits, the substitute clock, f
Time Base clock, f
to provide a substitute clock for the microcontroller just after a wake-up has occurred to enable faster
wake-up times. Together with f
The f
There are six different modes of operation for the microcontroller, each one with its own special
characteristics and which can be chosen according to the specific performance and power
requirements of the application. There are two modes allowing normal operation of the
microcontroller, the NORMAL Mode and SLOW Mode. The remaining four modes, the SLEEP0,
SLEEP1, IDLE0 and IDLE1 Mode are used when the microcontroller CPU is switched off to conserve
power.
TBC
clock is used as a source for the Time Base interrupt functions and for the TMs.
CPU
On
On
On
Off
Off
Off
H
/2~f
TBC
H
/64. Note that when the system clock source f
. These internal clocks are sourced by the LIRC oscillator. The f
SYS
f
H
~ f
/4 it is also used as one of the clock sources for the Watchdog timer.
f
Off
On
Off
Off
SYS
f
L
H
/64
30
Enhanced I/O Flash Type MCU
Description
HT68F13/HT68F14/HT68F15
f
On
On
On
On
Off
On
SUB
H
or low frequency f
L
. If f
H
SYS
~f
L
is selected, then it can be sourced
is switched to f
H
/64 for peripheral circuit to use.
On/Off
On
On
On
Off
On
f
S
L
source and is selected
L
February 9, 2011
from f
SUB
clock is used
SUB
f
On
On
On
On
Off
Off
TBC
H
, the high
, and the