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Infared Communications Controller (IrCC)
The Infared Communications Controller is fully compliant to the IrDA Specification Version 1.1 which
includes data rates up to 4Mbps meaning that IrDA-SIRA, IrDA-SIRB, IrDA-HDLC and IrDA-FIR
modes are all supported. In addition the IrCC provides support for ASK-IR, Consumer (TV remote)
IR, and RAW-IR (Host controller has direct access to the IR bit stream from/to the transceiver
module).
It is important to note that the IrCC block is a superset of UART2.
Thus the IrCC
comprises of a UART2 Asynchronous Communications Engine (ACE) and a separate Synchronous
Communications Engine (SCE) to provide the full set of IR modes as well as the standard UART
Com mode.
The IrCC block details are fully described in SMC’s specification titled “Infared
Communications Controller” Rev 1.30 dated November 1, 1995. The information in this section of the
specification will provide details on the integration of the FIR logic block into the FDC37C957FR
device.
The infrared interface provides a two-way wireless communications port using infrared as a
transmission medium. The IR transmission can use the standard UART2 TX and RX pins or optional
IRTX2 and IRRX2 pins. These can be selected through the configuration registers.
IrDA-SIR allows serial communication at baud rates up to 115K Baud. 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 sending a 500KHz
waveform for the duration of the serial bit time. A one is signaled by sending no transmission 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 transfered during a transmission and blocks the receiver
input until the time-out 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 time-out is four character
times. A character time is defined as 10 bit times regardless of the actual word length being used.