XR16L2550 Datasheet, PDF (17/45 Pages) Exar Corporation – LOW VOLTAGE DUART WITH 16-BYTE FIFO

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REV. 1.0.0
XR16L2550
LOW VOLTAGE DUART WITH 16-BYTE FIFO
2.16 Infrared Mode
The L2550 UART includes the infrared encoder and decoder compatible to the IrDA (Infrared Data Association)
version 1.0. The IrDA 1.0 standard that stipulates the infrared encoder sends out a 3/16 of a bit wide HIGH-
pulse for each “0” bit in the transmit data stream. This signal encoding reduces the on-time of the infrared LED,
hence reduces the power consumption. See Figure 12 below.
The infrared encoder and decoder are enabled by setting MCR register bit-6 to a ‘1’. When the infrared feature
is enabled, the transmit data output, TX, idles at logic zero level. Likewise, the RX input assumes an idle level
of logic zero from a reset and power up, see Figure 12.
Typically, the wireless infrared decoder receives the input pulse from the infrared sensing diode on the RX pin.
Each time it senses a light pulse, it returns a logic 1 to the data bit stream.
FIGURE 12. INFRARED TRANSMIT DATA ENCODING AND RECEIVE DATA DECODING
C h a ra cte r
Data Bits
TX Data 0 ¹ 0 ¹ 0 0 ^{1 1} 0 ¹
Transm it
IR Pulse
(TX Pin)
Receive
IR Pulse
(RX pin)
Bit Tim e
3/16 Bit Tim e
Bit Time
1/16 Clock Delay
1/2 Bit Tim e
IrEncoder-1
RX Data
0 1 0 1 0 0 11 0 1
Data Bits
Character
IRdecoder-1
17