xr16m2550 Exar Corporation, xr16m2550 Datasheet - Page 18

• Manufacturer Part Number: xr16m2550
• Description: High Performance Low Voltage Duart With 16-byte Fifo
• Manufacturer: Exar Corporation

XR16M2550
HIGH PERFORMANCE LOW VOLTAGE DUART WITH 16-BYTE FIFO
The M2550 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
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
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 M2550 has a provision to invert
the input polarity to accommodate this. In this case user can enable MCR bit-2 to invert the input signal.
2.17
Infrared Mode
F
IGURE
Receive
IR Pulse
(RX pin)
RX Data
TX Data
Transmit
IR Pulse
(TX Pin)
11. I
NFRARED
0
Bit Time
Bit Time
0
1
1/16 Clock Delay
T
RANSMIT
1
0
Figure
0
1
Character
Data Bits
D
11.
1
ATA
0
18
3/16 Bit Time
Data Bits
Character
0
E
0
Figure 11
NCODING AND
0
1
1 1
1
below.
0
R
0
ECEIVE
1/2 Bit Time
1
1
IRdecoder-
IrEncoder-1
D
ATA
D
ECODING
REV. 1.0.2