EZ80L92MCU Datasheet, PDF (138/241 Pages) Zilog, Inc. – eZ80Acclaim Flash Microcontrollers

eZ80L92 MCU
Product Specification
123
the section covering the Universal Asynchronous Receiver/Transmitter, on page 104, for
more information about the UART and its Baud Rate Generator.
Transmit
The data to be transmitted via the IR transceiver is first sent to UART0. The UART trans-
mit signal (TxD) and Baud Rate Clock are used by the infrared encoder/decoder to gener-
ate the modulation signal (IR_TXD) that drives the infrared transceiver. Each UART bit is
16-clocks wide. If the data to be transmitted is a logical 1 (High), the IR_TXD signal
remains Low (0) for the full 16-clock period. If the data to be transmitted is a logical 0, a
3-clock High (1) pulse is output following a 7-clock Low (0) period. Following the 3-
clock High pulse, a 6-clock Low pulse completes the full 16-clock data period. Data trans-
mission is illustrated in Figure 25. During data transmission, the IR receive function
should be disabled by clearing the IR_RXEN bit in the IR_CTL reg to 0. This prevents
transmitter to receiver cross-talk.
Baud Rate
Clock
16-clock
period
UART_TxD
IR_TxD
7-clock
delay
Start Bit = 0
3-clock
pulse
Data Bit 0 = 1 Data Bit 1 = 0 Data Bit 2 = 1 Data Bit 3 = 1
Figure 25. Infrared Data Transmission
Receive
Data received from the IR transceiver via the IR_RXD signal is decoded by the infrared
encoder/decoder and passed to the UART. The IR_RXEN bit in the IR_CTL register must
be set to enable the receiver decoder. The SIR data format uses half duplex communica-
tion therefore the UART should not be allowed to transmit while the receiver decoder is
enabled. The UART Baud Rate Clock is used by the infrared encoder/decoder to generate
the demodulated signal (RxD) that drives the UART. Each UART bit is 16-clocks wide. If
the data to be received is a logical 1 (High), the IR_RXD signal remains High (1) for the
full 16-clock period. If the data to be received is a logical 0, a 3-clock Low (0) pulse is
PS013012-1004
PRELIMINARY
Infrared Encoder/Decoder