CS22250 Wireless 10BT Controller

7 of 32

DS551PP2

Rev. 3.0

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3.2

Digital Wireless Radio Interface

The CS22250 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 a per packet basis without ARM intervention. This significantly

improves the performance of the system.

There are three primary digital interface ports for the CS22250 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 code encoding 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, 239) code implemented by the

CS22250 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 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.

3.4

High Speed Parallel Interface

This optional connectivity interface is the extension of the ARM control bus brought

outside of the CS22250 chip. In order to reduce the pin count, address and data are

multiplexed in a 32-bit address/data External Control Bus. For ease of connecting other

devices to the CS22250, this bus runs at half the speed of the internal ARM control bus.

The external control Bus interface exchanges data with the main memory via DMAC

(DMA controller block). This functional block supports two DMA engines for full duplex

operation. Moreover, one external interrupt pin is supported.