CS22220 datasheet(6/34 Pages) CIRRUS

6 / 34 page

CS22220 Wireless PCMCIA Controller

6 of 34

DS557PP2

Rev. 3.0

www.cirrus.com

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 tobefrom 20to255,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 Datasheet(PDF) 6 Page - Cirrus Logic