xr17c152im Exar Corporation, xr17c152im Datasheet - Page 30

• Manufacturer Part Number: xr17c152im
• Description: 5v Pci Bus Dual Uart
• Manufacturer: Exar Corporation

XR17C152
5V PCI BUS DUAL UART
Each UART in the 152 includes the infrared encoder and decoder compatible to the IrDA (Infrared Data
Association) version 1.0. The input pin ENIR conveniently activates both UART channels to start up in the
infrared mode. 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 its
receiver while the transmitter is sending data. This prevents the echoed data from going to 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[1:0], would
idle at logic zero level. Likewise, the RX[1:0] inputs assume an idle level of logic zero.
The infrared encoder sends out a 3/16 of a bit wide 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 15
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 RX input signal may be inverted prior delivered to
the input of the decoder via internal register setting. This option supports active low instead of normal active
high pulse from some infrared modules on the market.
4.5
Infrared Mode
below.
F
IGURE
TX D ata
Transm it
(TX Pin)
IR Pulse
Receive
IR Pulse
(RX pin)
RX Data
15. I
NFRARED
0
T
RANSMIT
Bit Tim e
Bit Tim e
1
0
1/16 Clock Delay
1
0
D
ATA
0
1
E
C haracter
D ata Bits
NCODING AND
1
0
30
Data Bits
3/16 Bit Tim e
Character
0
0
0
1
R
1
ECEIVE
1
1
D
0
0
ATA
1
D
1
1/2 Bit Tim e
ECODING
IRdecoder-1
IrEncoder-1
áç
áç
áç
áç
REV. 1.2.0