INFRARED INTERFACE
The infrared interface provides
wireless communications port using infrared as
transmission medium. Two IR
implementations have been provided for the
second UART in this chip (logical device 5),
IrDA and Amplitude Shift Keyed IR. The IR
transmission can use the standard UART2
TXD2 and RXD2 pins or optional IRTX and
IRRX pins. These can be selected through the
configuration registers.
a
two-way
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.
a
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.
IrDA 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 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
80
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