XR16L570 Datasheet, PDF (16/46 Pages) Exar Corporation – SMALLEST 1.62V TO 5.5V UART WITH 16-BYTE FIFO AND POWERSAVE

XR16L570
SMALLEST 1.62V TO 5.5V UART WITH 16-BYTE FIFO AND POWERSAVE
xr
REV. 1.0.0
2.17 Infrared Mode
The L570 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. However, this is not true with some
infrared modules on the market which indicate a logic 0 by a light pulse. So the L570 has a provision to invert
the input polarity to accommodate this. In this case, the user can enable MCR bit-2 to invert the IR signal at the
RX pin.
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)
Bit Time
3/16 Bit Time
1/2 Bit Time
IrEncoder-1
Receive
IR Pulse
(RX pin)
RX Data
Bit Time
1/16 Clock Delay
0 1 0 1 0 0 11 0 1
Data Bits
Character
IRdecoder-
16