Radiometrix Ltd

PLT/PLR Data Sheet

page 2

PLT / PLR data packet link radios

The PL modules use the hardware of the existing LMT/LMR transmitter receiver pair, combined with

completely new firmware to produce a simple to use but readily controllable data link

Both radios have a similar pinout. The bidirectional DATA pin requires an inverted RS232 data interface, at

3V CMOS logic levels (Both DATA and FLOW are bidirectional. As outputs they are open drain pins with 50K

pullups to the internal Vcc, and 470 series protection resistors. Do not exceed 3v on these pins).

The CMD pin selects the operating mode: If pulled low, then serial data is routed to a command interpreter

(see 'programming') . If high (floating) then received bytes are loaded into the buffer (the PLR receiver only

inputs data in command mode of course).

When the buffer is full, the transmitter either sends a databurst immediately, or waits for a command from the

user

The transmitter data buffer size is pre-set by a user command (from 1-32 bytes)

The data format uses is modified biphase at a peak data rate of 2500 bits per second.

Each burst consists of a framing sequence, a two byte address, a two byte checksum, and a variable length

(1-32 bytes) data 'payload'. The payload length information is coded into the framer sequence.

Minimum length (1 byte) bursts take about 70mS (including all transmitter setup and power on/off timings),

while a full 32 byte burst requires over 250mS.

Data transfer rate is limited by the interface's inability to receive data while transmitting a burst (if FLOW is

high, then the PLT is not listening to the serial port at all), or to decode received packets while in the process

of outputting one

The standard products use a 9600 baud user interface speed. Slower versions are also available (1200,

2400 and 4800 baud, with suffixes -1, -2, and -4). The baud rate is not user programmable.