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PT2215 V1.1

- 6 -

April, 2006

Infrared Remote Control Transmitter IC

PT2215

TIMING GENERATOR

The timing generator diagram is shown in the figure below. The oscillation frequency value is 432KHz

or 4MHz. The timing generator is terminated when no key is activated, however, it commences when a

key is pressed.

As you can see from the diagram above, the CLK1 (Oscillator Output) is divided by either 111 (for

4MHz) or by 12 (for 432KHz) depending on your mask option. CLK2 is used to control timer clocking.

The frequency of CLK2 is 36KHz and its inverse is used to generate the output pulses in the subcarrier

frequnecy. The duty factor may either be 25% or 33% depending on the mask option.

The control timer provides the timing of the key scanning, ROM access and Code transmission. The

length of the control timer is 4,096 subcarrier (pulse) periods which is equivalent to the transmission

repetition time. One bit time is equal to 64 pulse while on repetition time has 64 bit times. When the

control timer has arrived at a certain state and no key has been pressed, a stop signal is generated

which will terminate the oscillator. All drives will then be set to “LOW”. Pressing a key will set one of the

sense lines to “0” and this will generate a start signal which will restart the oscillator.

PULSE OUTPUT

The remote control word bits (as indicated by the addressed ROM locations) are stored into a shift

register every bit-time this register is shifted. The output is used to generate either “0” or “1” in the

biphase (Manchester) coding modulated with a 36KHz frequency. The duty factor of the modulation

pulses may be optionally selected to be either 25% or 33.3%. The pulse generator output controls the

output driver that provides the maximum current of 45mA.