xr20v2172 Exar Corporation, xr20v2172 Datasheet - Page 19

• Manufacturer Part Number: xr20v2172
• Description: Two Channel I2c/spi Uart With 64-byte Fifo And Rs232 Transceiver
• Manufacturer: Exar Corporation

REV. 1.0.0
The L402 includes an infrared encoder and decoder compatible to the IrDA (Infrared Data Association) version
1.0 and 1.1. 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 with a data rate up to 115.2 Kbps. For the IrDA 1.1 standard,
the infrared encoder sends out a 1/4 of a bit time wide HIGH-pulse for each "0" bit in the transmit data stream
with a data rate up to 1.152 Mbps. This signal encoding reduces the on-time of the infrared LED, hence
reduces the power consumption. See
The infrared encoder and decoder are enabled by setting MCR register bit-6 to a ‘1’. With this bit enabled, the
infrared encoder and decoder is compatible to the IrDA 1.0 standard. For the infrared encoder and decoder to
be compatible to the IrDA 1.1 standard, EFCR bit-7 will also need to be set to a ’1’. When the infrared feature
is enabled, the transmit data output, TX, idles LOW. Likewise, the RX input also idles LOW, see
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.
The Infrared Mode can only be used with channel B of the L402 using the TXB output and the RXB input pins.
2.16
Infrared Mode (UART Channel B Only)
F
IGURE
TX Data
Transmit
Receive
IR Pulse
(RX pin)
RX Data
IR Pulse
(TX Pin)
TWO CHANNEL I2C/SPI UART WITH 64-BYTE FIFO AND RS232 TRANSCEIVER
13. I
NFRARED
0
Bit Time
Figure 13
1
Bit Time
0
T
1/16 Clock Delay
RANSMIT
0
1
0
1
below.
Character
Data Bits
D
1
0
Data Bits
ATA
Character
19
3/16 or 1/4
Bit Time
0
0
E
NCODING AND
0
1
1 1
1
0
R
0
ECEIVE
1
1/2 Bit Time
1
IRdecoder-1
IrEncoder-1
D
ATA
D
ECODING
XR20V2172
Figure
13.