DS800-4 July ’07

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Radio Encoder / Decoder IC’s

RF800

System Operation:

The RF800 is can be set to either encoder mode or decoder mode of operation. In all cases transmitters must

be learnt to the RF800 decoder before any outputs will operate, thus enabling a secure telemetry system to be

built with the possibility of several systems operating within a local environment.

Achieving Optimum Range

Range is dependant on many factors including:

1.

RF Power output.

2.

Receiver sensitivity.

3.

Antenna efficiency.

4.

Local environmental conditions and any local Interference.

Given that there is a legal maximum power output which can be transmitted, and a limit on the sensitivity of the

receiver (usually constrained by cost), and that the antenna can never achieve 0dB loss (100% efficiency), then

the data type is an important aspect of the design.

The RF800 devices use a fully balanced Manchester encoded data protocol designed for optimum use of the

radio transmission path. This results in reduced bit errors and therefore ensures maximum range.

The data format automatically includes a pre-amble, synchronisation header, followed by the encrypted and

fixed code data then a CRC check. The RF800 data packet contains a total of 150 bits, which takes 30ms to

transmit when the RF800 is set to 200us element time. Thus if the element time is set to 400us it takes a total

of 60ms to transmit one data packet.

Each RF800 is programmed at the time of manufacture with a unique 16-bit serial number, which provides a

secure way of addressing RF800 devices. This provides upto 65,536 possible addresses.

Compatibility with 200 series Transmitters:

Acting as a decoder the RF800 is compatible with the 200 series

of ready to operate transmitter encoders (such as the 204 handset

as shown right).

To be compatible the RF800 must be setup as a decoder and

have its element time set to 400us. This enables designers to

easily integrate a remote control function into an application using

a ready made transmitter.