CS22220 Datasheet, PDF (6/34 Pages) Cirrus Logic – WIRELESS PCI/USB CONTROLLER

3.2 Digital Radio Interface
The CS22220 digital radio MAC I/F supports multiple radio baseband and RF interfaces.
The baseband registers can be programmed during the configuration time using the control
port interface. The MAC also provides the capability of programming the signal, service and
length on per packet basis without ARM intervention. This significantly improves the
performance of the system.
There are three primary digital interface ports for the CS22220 that are used for
configuration and during normal operation.
These ports are:
• The Control Port, which is used to configure, set power consumption modes, write
and/or read the status of the radio base band registers.
• The TX Port, which is used to output the data that needs to be transmitted from the
network processor.
• The RX Port, which is used to input the received demodulated data to the network
processor
3.3 FEC Codec
The FEC codec performs Reed-Solomon coding to protect the data before it is transmitted
to a noisy channel. It is a similar code as employed by the digital broadcast industry, such
as ITU-T J.83 for DVB. The RS(255, 8) code implemented by the CS22220 can reduce
error probability to 1/10e-9 in a typical 1/10e-3 error rate environment. The
encoder/decoder can be programmed to vary the coding block length (N) and correctable
error (t) to optimize the tradeoff between channel utilization and data protection. The range
of N is currently set to be from 20 to 255, and the t is 8. The symbol size is fixed at 8 bits.
Coding parameters can be set real time, allowing maximum flexibility for the system to
adjust the FEC setting, such as block size, in order to optimize channel efficiency. The
encoder also has a very low latency of two cycles. Both the encoder and decoder are fully
pipelined in structure to achieve single cycle throughput. The FEC can be disabled in
firmware.
CS22220 Wireless PCMCIA Controller
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