TMPR3911 datasheet(234/462 Pages) TOSHIBA

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Chapter 10 IR Module

10-4

10.3 Two-Way Communication Via IR

10.3.1

Requirements

The Communication Interface is implemented using a standard UART protocol, consisting of a start

bit, 8 bits of data (LSB first), then a stop bit. The data rate is adjustable using a programmable baud rate

counter. The Communication Interface consists of both a transmitter and a receiver and the UART is

operated half-duplex in one direction at a time. The UARTB Module is used for both the FSK and IrDA

data communication modes and contains DMA support for transmit and receive data (see Section 16 for

a detailed description of the UART Module).

For the FSK mode transmit direction, external communication IR analog circuitry encodes the

UARTB output data using an FSK modulation scheme, which modulates at two different frequencies

depending on whether the data is a “1” or a “0”. The carrier frequency is 1375 kHz and the mark and

space frequencies are 1325 kHz and 1425 kHz, respectively. For the receive direction, external

communication IR analog circuitry amplifies the received photo-diode signal and demodulates and

decodes the FSK signal before feeding the UARTB input. The transmitter and receiver portions of the

external communication IR analog circuitry contain individual power-down control for power

management purposes. The FSK communication mode operates at a data rate of 2400 to 38400 bps at 3

meters.

For the IrDA mode transmit direction, the UARTB output data directly drives the external analog

LED circuit. For the receive direction, the received photo-diode signal is externally amplified before

feeding the UARTB input. Additional control bits in the UART Module also allow for various narrow

pulse options to support the IrDA 1.0 standard. When configured for these options, the UART transmit

output pulses are narrower than normal and the UART receiver circuit also expects the same narrow

pulse format for the input data. The IrDA communication mode operates at a data rate up to 115.2 kbps

at 1 meter.

TMPR3911 Datasheet(PDF) 234 Page - Toshiba Semiconductor