TTP255 datasheet(11/49 Pages) TONTEK

11 / 49 page

Preliminary

TTP255

TonTouch

12’/08/21

Page 11 of 49

Ver3.0

§ System function description:

S-1: System Oscillators

The high speed oscillator can be operated in 3 different oscillator

modes; resonator mode, RC mode & external clock mode. The oscillator

mode can be defined by mask option.

Resonator/crystal mode (400K Hz~8M Hz oscillator)

A 400K Hz~8M Hz crystal across OSCI and OSCO pads, capacitors are

connected between OSCI/OSCO pads and ground (VSS).

RC mode (150KHz~4MHz oscillator, built-in mode fixed 4MHz)

The external resistor connected OSCI and the other end ground to

VSS. The recommend value of Rext between 60K and 500K , if used Rext

value too low (under 2K ), the oscillator will become unstable or stop. On

the other hand, if used Rext value too high (over 1M ), the oscillator will

easily be interfered by external radiation. OSCH/4 output signal is the internal

oscillating RC clock divided by 4 and keeps at high level during system reset.

External clock mode (DC~8MHz)

The oscillator supports the external clock direct input (OSCI). For the

clock source directly drives the crystal oscillator input, so it needs the same

wake up time (OST) as crystal mode from power on or power saving mode.

S-2: Peripheral Oscillators

The low speed oscillator was built-in an internal RC oscillator that is for

low power consumption consideration and fixed peripheral device timing

control. The peripheral oscillator provides three models for user’s selection,

but the target peripheral oscillator frequency is set about 16 KHz. The

external R mode is just for micro-adjustment for more accurate 16 KHz

frequency.

Built-in RC oscillator and the frequency range between 12 KHz ~ 22 KHz.

S-3: CPU clock

The CPU clock comes from system/peripheral oscillator which was

controlled by H/L bit in PS register. In the normal operation, the system

clock comes from high speed system oscillator (OSCH/2). The low speed

operation frequency (OSCL/2) comes from RC oscillator was selected by

mask option.

TTP255 Datasheet(PDF) 11 Page - Tontek Design Technology