ZLP12840 datasheet(53/58 Pages) ZILOG

53 / 58 page

PS024406-0106

P R E L I M I N A R Y

Infrared Learning Amplifier

ZLP12840 OTP MCU

Product Specification

Infrared Learning Amplifier

The ZLP12840 MCUs infrared learning amplifier allows the user to detect and decode

infrared transmissions directly from the output of the receiving diode without the need for

external circuitry. See Port 3 on page 14.

An IR diode can be connected to the IR amp as shown in Figure 12. When the IR amp is

enabled and an input current is detected on Port 3, pin 1 (P31), the IR amp outputs a logi-

cal High value. When the input current is below the switching threshold of the IR amp, the

amp outputs a logical Low value.

Within the MCU, the IR amp output goes to the capture/timer logic, which can be pro-

grammed to demodulate the IR signal. The IR amp output can also be read by the CPU, or

drive the Port 3, pin 4 (P34) output if write-only register bit PCON[0] is written with a 1.

The IR learning amp can demodulate signals up to a frequency of 500 KHz. A special

mode exists that allows the user to capture the third, fourth, and fifth edges of the IR amp

output and generate an interrupt.

See Timers on page 57 for details about programming the timers to demodulate a received

signal.

Figure 12. Learning Amplification Circuitry with the ZLP12840 MCU

VCC

Photodiode

P31 of MCU

ZLP12840 Datasheet(PDF) 53 Page - Zilog, Inc.