DS601-2

11

©2003 Reg. No. 227 4001, ENGLAND

Page 5

Low-Power-Radio Transceiver IC

RF600T

Data Buffering

The device contains a 190 byte data buffer which is used to either buffer host data prior to transmission

over the radio link or alternately to buffer data received over the radio link before it is transmitted to the

host. Since this is a shared buffer the device can only operate in a half duplex manner - that is at a given

time data can either be received from the host and then transmitted over the radio link or data can be

received over the radio link and sent to the host but these functions cannot occur at the same time. Once

a character has been received from the host or once the start of a radio data packet has been sensed the

device will lock out the ‘other’ function until the first one has been completed.

Host Interface

The interface to the host device consists of the following signal and control lines:

TxH

Serial data from the host which is to be transmitted over the RF link. Idle mark ‘1’.

RxH

Serial data for the host which has been received over the RF link. Idle mark ‘1’.

CTS

Handshake line to the host. When ‘0’ tells the host that it is Clear To Send data to the RF600T for

transmission over the RF link.

RTS

Handshake line from the host. When ‘0’ tells the RF600T that the host is making a Request To

Send data to the host.

Host Communications

All host communications are carried out using the following asynchronous serial format.

8 data bits.

1 stop bit.

No parity.

The host baud rate is selected using the HBAUD option as described above.

Host Data Flow Control

Serial data from the host which is to be sent over the radio link is input at TTL level on the TxD pin. When

the device is ready to receive data, the CTS line from the device will be low and up to 190 data bytes will

be accepted and stored in the internal data buffer. When the buffer becomes full the CTS line will be taken

high and the host must then stop transmitting. In order to allow for host UART’s which have an output

FIFO buffer, a further 4 characters will be accepted after the CTS line has been asserted. In the event that

the flow of data characters is not contiguous and an idle period of 20 ms occurs in the data stream then

the CTS line will be asserted high to signify that the host should stop sending further data. In this case the

current buffer contents will make up the next data packet to be sent over the radio link.

Serial data which has been received over the radio link will be checked for correct Manchester coding and

CRC checksum (and address match if in addressed mode) before this data is transmitted at TTL level on

the RxH pin. Data flow to the host is controlled by the RTS line from the host. When this line is low, data in

the buffer will be transmitted to the host. When the RTS line is taken high then data flow will be inhibited

and until the buffer is empty the device will not be able to perform any other operations.