1. FUNCTIONAL DESCRIPTION
On receipt of a packet downloaded by the Host, the FFRPC2 will append to the packet: Preamble, start
byte and a error check code. The packet is then coded for security and mark:space balance and
transmitted through the BiM2 Transceiver as a 160kbps synchronous stream. One of four methods of
collision avoidance (listen before TX) may be user selected.
When not in transmit mode, the FRPC2 continuously searches the radio noise for valid preamble. On
detection of preamble, the FRPC2 synchronises to the in-coming data stream, decodes the data and
validates the check sum. The Host is then signalled that a valid packet is waiting to be unloaded. The
format of the packet is entirely of the users determination except the 1st byte (the Control Byte) which
must specify the packet type (control or data) and the packet size. A valid received packet is presented
back to the host in exactly the same form as it was given.
To preserve versatility, the FRPC2 does not generate routing information (i.e.
source/ destination addresses) nor does it handshake packets. These network
specific functions should be performed by the host.
Additional features of the FRPC2 include extensive diagnostic/debug functions for evaluation and
debugging of the radio and host driver software, a built in self test function and a sleep mode / wake-up
mechanism which may be programmed to reduce the average current to less than 100µA. The operating
parameters are fully programmable by the host and held in EEPROM, the host may also use the
EEPROM as a general purpose non-volatile store for addresses , routing information etc.
1.1 OPERATING STATES
The FRPC2 has four normal operating states:
•
•
•
•
IDLE / SLEEP
HOST TRANSFER
TRANSMIT
RECEIVE
IDLE/SLEEP
The IDLE state is the quiescent/rest state of the FRPC2. In IDLE the FRPC2 enables the receiver
and continuously searches the radio noise for message preamble. If the power saving modes
have been enabled the FRPC2 will pulse the receiver on, check for preamble and go back to
SLEEP if nothing is found. The 'ON' time is 2.5ms, OFF time is programmable in the FRPC2’s
EEPROM and can vary between 22ms and 181ms. The TX Request line from the Host is
constantly monitored and will be acted upon if found active (low). A TX Request will
immediately wake the FRPC2 up from SLEEP mode.
HOST TRANSFERS
If the host sets the TX Request line low a data transfer from the Host to the FRPC2 will be
initiated. Similarly the FRPC2 will pull RX Request low when it requires to transfer data to the
Host (this may polled or used to generate a Host interrupt).
The transfer protocol is fully asynchronous, i.e. the host may service another interrupt and then
continue with the FRPC2 transfer. It is desirable that all transfers are completed quickly since
the radio transceiver is disabled until the Host <> FRPC2 transfer is completed. Typically a fast
host can transfer a 60 byte packet to / from the FRPC2 in under 1ms.
Radiometrix Ltd, FRPC2
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RADIOMETRIX [ RADIOMETRIX LTD ]
