Advanced I/O Controller with Motherboard GLUE Logic
Datasheet
7.2
Infrared Interface
The infrared interface provides a two-way wireless communications port using infrared as a transmission
medium. Several IR implementations have been provided for the second UART in this chip, IrDA, HP-SIR
and Amplitude Shift Keyed IR. The IR transmission can use the standard UART2 TXD2 and RXD2 pins or
optional IRTX2 and IRRX2 pins. These can be selected through the configuration registers.
IrDA 1.0 allows serial communication at baud rates up to 115.2 kbps. Each word is sent serially beginning
with a zero value start bit. A zero is signaled by sending a single IR pulse at the beginning of the serial bit
time. A one is signaled by sending no IR pulse during the bit time. Please refer to the AC timing for the
parameters of these pulses and the IrDA waveform.
The Amplitude Shift Keyed IR allows asynchronous serial communication at baud rates up to 19.2K Baud.
Each word is sent serially beginning with a zero value start bit. A zero is signaled by sending a 500KHz
waveform for the duration of the serial bit time. A one is signaled by sending no transmission during the bit
time. Please refer to the AC timing for the parameters of the ASK-IR waveform.
If the Half Duplex option is chosen, there is a time-out when the direction of the transmission is changed.
This time-out starts at the last bit transferred during a transmission and blocks the receiver input until the
timeout expires. If the transmit buffer is loaded with more data before the time-out expires, the timer is
restarted after the new byte is transmitted. If data is loaded into the transmit buffer while a character is
being received, the transmission will not start until the time-out expires after the last receive bit has been
received. If the start bit of another character is received during this time-out, the timer is restarted after the
new character is received. The IR half duplex time-out is programmable via CRF2 in Logical Device 5. This
register allows the time-out to be programmed to any value between 0 and 10msec in 100usec
increments.
IR Transmit Pins
The following description pertains to the TXD2 and IRTX2 pins of the LPC47M182.
Following a VCC POR, the TXD2 and IRTX2 pins will be output and low. They will remain low until one of
the following conditions are met:
IRTX2 Pin:
This pin will remain low following a VCC POR until serial port 2 is enabled by setting the activate bit, at
which time the pin will reflect the state of the IR transmit output of the IRCC block.
TXD2 Pin:
This pin will remain low following a VCC POR until serial port 2 is enabled by setting the activate bit, at
which time the pin will reflect the state of the IR transmit output of the IRCC block (if IR is enabled through
the IR Option Register for Serial Port 2).
This pin will remain low following a VCC POR until serial port 2 is enabled by setting the activate bit, at
which time the pin will reflect the state of the transmit output of serial port 2.
Revision 1.8 SMSC/Non-SMSC Register Sets (02-24-05)
94
SMSC LPC47M182
DATASHEET
SMSC [ SMSC CORPORATION ]
