Irda Operation - Hitachi H8S/2378, H8S/2378R Series Hardware Manual

15.8

IrDA Operation

When the IrDA function is enabled with bit IrE in IrCR, the SCI_0 TxD0 and RxD0 signals are
subjected to waveform encoding/decoding conforming to IrDA specification version 1.0 (IrTxD
and IrRxD pins). By connecting these pins to an infrared transceiver/receiver, it is possible to
implement infrared transmission/reception conforming to the IrDA specification version 1.0
system.
In the IrDA specification version 1.0 system, communication is started at a transfer rate of 9600
bps, and subsequently the transfer rate can be varied as necessary. As the IrDA interface in this
LSI does not include a function for varying the transfer rate automatically, the transfer rate setting
must be changed by software.
Figure 15.33 shows a block diagram of the IrDA function.
TxD0/IrTxD
RxD0/IrRxD
Transmission: In transmission, the output signal (UART frame) from the SCI is converted to an
IR frame by the IrDA interface (see figure 15.34).
When the serial data is 0, a high pulse of 3/16 the bit rate (interval equivalent to the width of one
bit) is output (initial value). The high-level pulse can be varied according to the setting of bits
IrCKS2 to IrCKS0 in IrCR.
In the specification, the high pulse width is fixed at a minimum of 1.41 µs, and a maximum of
(3/16 + 2.5%) × bit rate or (3/16 × bit rate) + 1.08 µs. When system clock ø is 20 MHz, 1.6 µs can
be set for a high pulse width with a minimum value of 1.41 µs.
IrDA
Pulse encoder
Pulse decoder
IrCR
Figure 15.33 Block Diagram of IrDA
SCI0
TxD
RxD
Rev. 1.0, 09/01, page 695 of 904