Datasheet

TIR1000, TIR1000I
STANDALONE IrDA ENCODER AND DECODER
SLLS228F – DECEMBER 1995 – REVISED JULY 1999
5
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
IrDA encoder function (continued)
It is possible for jitter or slight frequency differences to cause the next falling edge on IR_RXD to be missed for
one 16XCLK cycle. In that case, a 1-clock-wide pulse appears on U_RXD between consecutive zeroes. It is
important for the UART to strobe U_RXD in the middle of the bit time to avoid latching this 1-clock-wide pulse.
The TL16C550C UART already strobes incoming serial data at the proper time. Otherwise, note that data is
required to be framed by a leading zero and a trailing one. The falling edge of that first zero on U_RXD
synchronizes the read strobe. The strobe occurs on the eighth 16XCLK pulse after the U_RXD falling edge and
once every 16 cycles thereafter until the stop bit occurs.
1 2 3 4 5 6 7 8 10 12 14 16 1 2 3 4 5 6 7 8 10 12 14 16
IR_RXD
16XCLK
U_RXD
Figure 6. Timing Causing 1-clock-wide Pulse Between Consecutive Ones
16 Cycles 16 Cycles
16 Cycles
7 Cycles
16XCLK
IR_RXD
U_RXD
External Strobe
Figure 7. Recommended Strobing For Decoded Data