xr20m1170 Exar Corporation, xr20m1170 Datasheet - Page 21

• Manufacturer Part Number: xr20m1170
• Description: I2c/spi Uart With 64-byte Fifo
• Manufacturer: Exar Corporation

REV. 1.0.0
The M1170 UART includes the 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 UART can be in the infrared mode upon power-up if the ENIR# pin is LOW. After power-up, the infrared
mode can be controlled via MCR bit-6.
2.15
Infrared Mode
F
IGURE
TX Data
Transmit
Receive
IR Pulse
(RX pin)
RX Data
IR Pulse
(TX Pin)
18. I
NFRARED
0
Bit Time
1
Bit Time
0
T
1/16 Clock Delay
RANSMIT
0
1
0
1
Character
Data Bits
D
1
0
Data Bits
ATA
Character
21
3/16 or 1/4
Bit Time
0
0
E
Figure 18
NCODING AND
0
1
1 1
1
below.
0
I2C/SPI UART WITH 64-BYTE FIFO
R
0
ECEIVE
1
1/2 Bit Time
1
IRdecoder-1
IrEncoder-1
D
ATA
D
ECODING
XR20M1170
Figure
18.