TIR1000, TIR1000I

STANDALONE IrDA

™ ENCODER AND DECODER

SLLS228F – DECEMBER 1995 – REVISED JULY 1999

4

POST OFFICE BOX 655303

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

2 34 56 7

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