Operation Guide

OG_LMD-401_v10e Circuit Design, Inc. 13

OPERATION GUIDE

TIMING CHART

Control timing in a typical application is shown in Figure 3.

Initial setting of the port connected to the radio module is performed when power is supplied by the CPU and

reset is completed. MOS-FET for supply voltage control of the radio module, RXSEL and TXSEL are set to

inactive to avoid unwanted emissions. The power supply of the radio module is then turned on. When the

radio module is turned on, the PLL internal resistor is not yet set and the peripheral VCO circuit is unstable.

Therefore data transmission and reception is possible 40 ms after the setting data is sent to the PLL at the

first change of channel, however from the second change of channel, the circuit stabilizes within 20 ms and is

able to handle the data.

Changing channels must be carried out in the receive mode. If switching is performed in transmission mode,

unwanted emission occurs.

If the module is switched to the receive mode when operating in the same channel, (a new PLL setting is not

necessary) it can receive data within 5 ms of switching

. For data transmission, if the RF channel to be used

for transmission is set while still in receiving mode, data can be sent at 5 ms after the radio module is

switched from reception to transmission

Check that the Lock Detect signal is “high” 20 ms after the channel is changed. In some cases the Lock

Detect signal becomes unstable before the lock is correctly detected, so it is necessary to note if processing

of the signal is interrupted. It is recommended to observe the actual waveform before writing the process

program.

DC offset may occur due to frequency drift caused by ambient temperature change. Under conditions

below -10 °C, 10 to 20 ms delay of DO output is estimated. The customer is urged to verify operation at low

temperature and optimize the timing.

Sending ‘10101…..’ preamble just after switching to transmission mode enables smoother operation of the

binarization circuit of the receiver. Preamble length: 15 ms (Typical) at -20 to + 65°C