RF620T
RF620R
SmartRadio Transmitter / Receiver
Serial Data Mode (mode pin pulled high via 10K resistor)
Operating mode
The RF620T transmitter has a serial data input and a /CTS handshake output which allows the
module to turn off input data flow if required. Serial data fed into the RF620T is stored in a 50 word
buffer and when this is full the /CTS handshake line is raised to indicate to the host system that it
should stop sending data. A further 5 words may be sent and are buffered without data corruption. In
the event that a shorter data packet than 50 words is input or if there is a long inter-word delay then
after data flow has ceased for 10 character times at the current baud rate the /CTS handshake will be
raised and the part packet immediately transmitted. After each data packet has been sent the
transmitter will only drop its /CTS output to enable host data flow when the data has been transmitted
over the radio path and when the associated RF620R has had time to output the data to its receiving
host.
The RF620R receiver has a serial data output and an /RTS handshake input which allows the
receiving host to turn off output data flow if required. It should be noted that this handshake must be
used with care since if it is held high (disabled) then received data may be lost. If it is not required to
use the \RTS handshake line it should be held at ground level.
Learn/erase procedure and auto baud function
The following procedure should be followed if it is required to learn an RF620T to an RF620R or if it is
required to use the auto baud function. This latter function allows the baud rate of the serial data input
to the RF620T to be set to any of the following rates: 1200, 2400, 4800, 9600* or 19200 bauds (*
indicates default setting). The format of the data stream is 8 data bits, 1 stop bit and no parity. Note
that at all times the baud rate of the associated RF620R module is the same as that of the RF620T
module since each data packet transmitted by the RF620T specifies its current host data rate and this
is used by the RF620R to set its serial data rate.
RF620T: The learn button is pressed, the learn LED will come on and then go off when the button is
released. After 2 seconds the unit will transmit a learn packet, display the current baud rate as a
series of LED flashes and then idle with the LED off for 5 seconds.
Current baud rate
LED flashes
19200
9600
4800
2400
1200
1
2
3
4
5
(default)
These functions will be repeated 20 times. If serial data is input to the unit then the auto-baud function
will be carried out and the revised baud rate displayed as a series of flashes. The auto-baud function
will only be carried out once in any given learn session and during auto-baud detection the host data
flow into the module should consist of a stream of characters at the desired baud rate and which lasts
for at least 10 seconds. It is recommended that for best performance of the auto-baud function that a
stream of the letter ‘R’ be sent.
RF620R: the learn button is pressed, the learn LED will come on and remain on when the button is
released. When a learn packet from an RF620T is received, the RF620T address will be saved to
eeprom in the RF620R and the LED will flash 5 times to indicate that the learn has been successful.
The mode will terminate after 60 seconds if no learn packet is received.
If it is required to erase the learned address in the RF620R then the learn button should be pressed and
held for more than 8 seconds and then released after which time the LED will flash rapidly to indicate
that erase of the address has taken place. Note that in this state the RF620R will respond to any
RF600T.
DS620-3 Jan ‘07
©2007 Reg. No. 227 4001, ENGLAND
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