User Manual

16 Quatech QTM-8524 Manual
1.3.4 Supporting Multiple Baud Rates
As noted earlier, QTM-8000 Series networks support devices operating at
different baud rates. For example, in Figure 1.3 the diagram depicts a wire-
less modem operating at 19200 bps, QTM-8000 Series modules operating at
2400 bps and a PLC operating at 9600 bps. The QTM-8520 converter module
can automatically switch to any baud rate in the 1200 bps to 115,200 bps
range.
In order to support multiple baud rates in a wireless network, the QTM-8520
must be used to auto tune the network and pairs of QTM-8524 RF modules
are jumper configured to match the specific baud rate at which downstream
modules are operating. When the host PC sends commands it tailors them
to the baud rate at which the target module is operating. The QTM-8520
drives the signal from RS-232 to RS-485 at that given baud rate. The QTM-
8524 that is configured for that same baud rate receives the RS-485 com-
mands and converts them to RF. Any other QTM-8524 set for a different
baud rate will ignore the command. The RF signal is transmitted along a set
channel as selected on the QTM-8524. The downstream QTM-8524 that is
configured for that same channel receives the RF signal and converts the
commands to RS-485. These commands are then distributed to all the mod-
ules downstream from the receiving QTM-8524. Each module at the target
baud rate will determine whether the command is addressed to it (see step 3
in section 1.3.3) and react appropriately.