XR16M598 Datasheet, PDF (20/58 Pages) Exar Corporation – 1.62V TO 3.63V HIGH PERFORMANCE OCTAL UART WITH 16-BYTE FIFO

XR16M598
1.62V TO 3.63V HIGH PERFORMANCE OCTAL UART WITH 16-BYTE FIFO
REV. 1.0.0
2.14 Infrared Mode
Each UART in the 598 includes the infrared encoder and decoder compatible to the IrDA (Infrared Data
Association) version 1.0. The input pin ENIR conveniently activates all 8 UART channels to start up in the
infrared mode. Note that the ENIR pin is sampled when the RST# input is de-asserted. This global control pin
enables the MCR bit-6 function in every UART channel register. After power up or a reset, the software can
overwrite MCR bit-6 if so desired. ENIR and MCR bit-6 also disable the receiver while the transmitter is
sending data. This prevents echoed data from reaching the receiver. The global activation ENIR pin prevents
the infrared emitter from turning on and drawing large amount of current while the system is starting up. When
the infrared feature is enabled, the transmit data outputs, TX[7:0], would idle at logic zero level. Likewise, the
RX [7:0] inputs assume an idle level of logic zero.
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 10 below.
The infrared decoder receives the input pulse from the infrared sensing diode on RX pin. Each time it senses a
light pulse, it returns a logic zero to the data bit stream. The decoder also accepts (when FCTR bit-4 = 1) an
inverted IR-encoded input signal. This option supports active LOW instead of normal active HIGH pulse from
some infrared modules on the market.
FIGURE 10. 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-
20