Smart Com Radio Transceiver IC
RF600T
be connected from Vcc to the learn pin, ensuring that the maximum current drawn by the LED (as given in
this data sheet) is not exceeded.
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 TxH 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
DS601-4
25th JUN 2004
©2004 Reg. No. 227 4001, ENGLAND
Page 5
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