RPC-UHF RADIOMETRIX [Radiometrix Ltd], RPC-UHF Datasheet - Page 18

• Manufacturer Part Number: RPC-UHF
• Description: Radio Packet Controller
• Manufacturer: RADIOMETRIX [Radiometrix Ltd]

A Detailed look at the RPC's transceiver interface
The RPC interfaces to the transceiver using 4 lines :-
TX
TXD
RX
RXD
note 1 All lines are 5V CMOS levels
note 2 There is no requirement for a carrier/signal detect signal from the transceiver nor for the RXD
The enable lines - TX & RX
These normally high, active low lines are used to control the transceiver. The RPC is a half-duplex
controller thus in normal operation the transceiver is either transmitting or receiving or off. The RPC
only enables the TX and the RX at the same time during self test (local loop back).
Transmit Data - TXD
TXD is the serial data to the transmitter, it is held low when the transmitter is not enabled. When the
TX is enabled a synchronous 40kbit/s (25.0µs/bit) serial code is present to modulate the transmitter.
Receive Data - RXD
RXD is a hi-impedance input which is fed with a 'squared-up' (5V logic level) signal from the receivers'
data slicer. The RPC contains a very selective, noise immune signal detector and therefor does not
require that the RXD signal be muted in the absence of signal, i.e.. squared-up channel noise may be
fed to the RPC when no signal is present.
The RPC's Packet Encoder
The packet is made-up of 4 parts:
Preamble
This is a simple 20kHz square wave, the number of cycles being programmed by address 01h of the
EEPROM. The preamble has two functions, the initial portion it is used to allow the data slicer in a
remote receiver to establish the correct slicing point (for the BiM-XXX-F this takes a maximum of
3ms), after the receiver has settled, the remaining portion is used by the receiving RPC to positively
identify and phase lock onto the incoming the signal (this requires 15 cycles of preamble). The
preamble may extended to wake-up a remote RPC in power saving mode.
Frame sync
A 7 bit Barker sequence is used to identify the start of the data. Alternatively if the transmitter is
sending extended preamble (to wake a power saving remote RPC) a complimented 7 bit Barker
sequence is sent every 256 preamble cycles as a 'Please Hold The Line' code. An 8th balancing bit is
added after the Barker sequence.
Radiometrix Ltd, RPC
PPENDIX
output to be muted when no signal is present.
output
output
output
input
Active low enable for the transmitter.
Serial data to be sent.
Active low enable for the receiver.
Received serial data.
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