Radiometrix Ltd

PLT/PLR Data Sheet

page 8

Operating principle

On recieve, the FLOW output goes high at least 400uS (typically 480uS) before beginning of the start bit of

the first byte out

it goes low again 12uS after the end of the last byte stop-bit

This output can be polled, or used as an interrupt, to detect the arrival of a data byte (or bytes)

(tx measurements made on 32byte bursts, default mode 'send on buffer full)

On transmit, the FLOW output goes high 80uS after the end of the 32nd byte

(about 25-30mS after this point, the tx keys up and starts sending the burst)

it returns to low when the transmitter has ramped fully down

A 32 byte burst takes around 250mS to send, from first byte into tx, to last out of rx

(it's about 218mS from the start of the first byte in to the FLOW output returning low)

For a 32 byte burst, FLOW is high for about 185mS

Although such asynchronous operation is not really recommended (especially for timing-uncertain devices

like PCs, and especially when running high level languages and/or multiple applications), it is also possible

to send a 32 byte burst roughly every 225mS, for an aggregate throughput of about 140 bytes per second

(1400 baud)

(this is not the intended operating mode for the devices, but it does give an idea of the capabilities)

It would be much better (if maximum data rate was wanted) to send a (32byte) burst when the FLOW output

is low

The MODE byte

This is a value stored in EEPROM, that selects the various operating functions of the radio. Be careful. By

setting this incorrectly you can disable your radio link

Factory default (send when buffer full, clear buffer on exit from setup mode) is selected by MVALUE 0

Functions of the mode byte bits.

Bit0

when zero the PLT will send when it's buffer is full

Bit1

when zero the PLT clears the data buffer on exit from command mode

Bit2

set:

send burst on entering command mode (if buffer has any data in it)

Bit3

set:

send burst on stop-bit over-run (ie: serial pin is low for more than 1.04mS)

Bit4

set:

clear data buffer on stop-bit over-run

Bit5

set:

send burst on receiving the character specified by SVALUE in the datastream

Bit6

set:

send burst if the gap following a character exceeds approx 4.2mS

Bit7

reserved

Additionally, there are a few command mode characters that can be used :

>

send burst (if data is present in the buffer)

<

clear data buffer

Obviously:

bit 3 and bit 4 should not be set at the same time

bit 1 should be set if a command mode controlled send is used with a 'bouncy' CMD drive

(switch)

if bit 2 is set then it doesn't matter what bit 1 is doing !

Bit 6 (timeout mode) is best used with BVALUE 32 and other bits inactive

To generate a stop-bit over-run, either pull down the serial input pin for over 1.04mS (1 byte at `

9600 baud),

Or send a 00 (null, CTRL @ character ) at a slower baud rate