DS0353-9 March ‘05

©2005 Reg. No. 227 4001, ENGLAND

Page 7

TRXQ1

RXQ1

TRXQ1 Operating Modes

The device is capable of operation in one of two modes, either broadcast or addressed. The following

description describes the features of these mode and assumes two TRXQ1 nodes ‘A’ and ‘B’. The RF600T

must be configured before power up for either the broadcast or addressed mode of operation by means of the

MODE pin. Note that for security, broadcast nodes will not receive data from addressed nodes

Broadcast mode.

This mode allows a host generated data block from node ‘A’ to be transmitted and received by any number of

other nodes. This data is received and verified (for correct Manchester coding and CRC) by the other nodes

before being output to their host devices. Alternately, in the same way the other nodes can send data to node

‘A’. Note that although any node can initiate a transfer, only one direction of transfer can be active at a given

time. Correct reception of a data packet is not acknowledged and the node hosts have the responsibility of

ensuring that data transfers occur as required by operating some form of message protocol over the half

duplex data link.

Addressed mode

This mode allows a host generated data block from node ‘A’ to be transmitted and for the data frame to be

addressed to one other network node – in this case we assume node ‘B’. When the data is received by node

‘B’ it is verified for correct Manchester coding, CRC and for address match and then an acknowledge

message is transmitted back to node ‘A’. Node ‘A’ then outputs a confirmation to the host in the form of the

ASCII character ‘C’ (Confirmed). Note that confirmation is given when the data block is stored in the buffer of

node ‘B’ and not when it has been delivered to the host at node ‘B’.

All message transfers are tagged with the addresses of both the origin and destination, thus ensuring secure

data transfer at all times. Either node ‘A’ or node ‘B’ can initiate a transfer but only one direction of transfer

can be active at a given time. In the event that the originating node does not get confirmation of receipt of the

data packet, the software re-tries the transfer five times after which node ‘A’ will output an error message to

the host in the form of the ASCII character ‘F’ (Failed).

Correct reception (or otherwise) of a data packet is thus acknowledged and the host devices are relieved of

most of the workload of ensuring that data transfers occur as required.

The RF600T must be configured before use for either the broadcast or addressed point to point mode of

operation and details of how this is carried out are given in the following section.

System Operation

Each RF600T is programmed at manufacture with a 24 bit serial number which uniquely identifies the device.

In an addressed point to point system, these serial numbers are used as the device address for the nodes in

the system and non-volatile eeprom memory in the device stores the address of the ‘other’ node in the system.

If, as at time of manufacture, no address has been stored in the device or if the address has been erased then

the device will only operate in the broadcast mode. If however an address has been stored then the device will

also be able to operate in the addressed point to point mode.