Datasheet

TIR1000, TIR1000I
STANDALONE IrDA ENCODER AND DECODER
SLLS228F – DECEMBER 1995 – REVISED JULY 1999
4
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
IrDA encoder function
Serial data from a UART is encoded to transmit data to the optoelectronics. While the serial data input to this
block (U_TXD) is high, the output (IR_TXD) is always low, and the counter used to form a pulse on IR_TXD is
continuously cleared. After U_TXD resets to 0, IR_TXD rises on the falling edge of the seventh 16XCLK. On
the falling edge of the tenth 16XCLK pulse, IR_TXD falls, creating a 3-clock-wide pulse. While U_TXD stays
low, a pulse is transmitted during the seventh to tenth clocks of each 16-clock bit cycle.
U_TXD
16XCLK
IR_TXD
1 234567 8 10 12 14 16
Figure 2. IrDA-SIR Encoding Scheme –
Detailed Timing Diagram
Figure 3. Encoding Scheme – Macro View
16XCLK
U_TXD
IR_TXD
16 Cycles 16 Cycles 16 Cycles 16 Cycles
IrDA decoder function
After reset, U_RXD is high and the 4-bit counter is cleared. When a falling edge is detected on IR_RXD, U_RXD
falls on the next rising edge of 16XCLK with sufficient setup time. U_RXD stays low for 16 cycles (16XCLK) and
then returns to high as required by the IrDA specification. As long as no pulses (falling edges) are detected on
IR_RXD, U_RXD remains high.
IR_RXD
16XCLK
U_RXD
1 2 3 4 5 6 7 8 10 12 14 16
Figure 4. IrDA-SIR Decoding Scheme –
Detailed Timing Diagram
Figure 5. Decoding Scheme – Macro View
16XCLK
IR_RXD
U_RXD
16 Cycles 16 Cycles 16 Cycles 16 Cycles