XR16L2551_07 Datasheet, PDF (19/49 Pages) Exar Corporation – LOW VOLTAGE DUART WITH POWERSAVE

XR16L2551
REV. 1.1.3
LOW VOLTAGE DUART WITH POWERSAVE
2.16 Infrared Mode
The L2551 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
Character
Data Bits
TX Data ^{0 1 0 1 0 0 1 1 0 1}
Transmit
IR Pulse
(TX Pin)
Receive
IR Pulse
(RX pin)
Bit Time
3/16 Bit Time
Bit Time
1/16 Clock Delay
1/2 Bit Time
IrEncoder-1
RX Data
0 1 0 1 0 0 11 0 1
Data Bits
Character
IRdecoder-
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