Configuring the M7 Data Radio for SCADA
For SCADA applications, configure the M7 radio as per the user manual. In most cases, the factory defaults are the best place to start. Set the frequency using the ATFX xxx.xxxx command to your system frequency. Then, based upon your system, configure the following parameters:
| ATBC | Enable/disable Busy Channel Lockout. Normally, the radio modem does not check for a busy channel. If you are running a large system, with asynchronous data on the radio channel, you should enable BCL so the modem does not transmit while another device is on the air. For polled systems, do not enable this feature. |
| ATCH | Enable/Disable hardware flow control. By default this is off and will work fine in most applications. Enabling hardware flow control will ensure that the modem buffers data and only outputs it to the user’s device or RTU when the device is ready to receive it. |
| ATFX | Used to set the radio frequency of the modem. |
| ATR2 | The over-the-air data rate. For long-range, set it at 4800bps. For lowest latency, set it at 8000bps or 9600bps. ATR2 3 for 4800baud. ATR2 4 for 8000 baud. |
| ATR3 | Serial port time out. This is the amount of idle-time (in mS) before the FireLine will begin to transmit a packet of data. When no data comes into the modem for this amount of time, the FireLine will transmit the contents of its data buffer over the air. The factory default setting is 20mS. For SCADA systems using MODBU, 2mS is suggested (ATR3 5). |
| ATMY | The M7 series modems have 16 bit IDs. Most SCADA systems work in a broadcast configuration, where all modems hear all other modems. Be sure to set the unit ID in each modem to a unique ID number, so that the duplicate packet filtering works properly. |
| ATMK | To turn off address filtering, and allow all units to receive data from all other units, set the net mask to all zeros (ATMK 0000). |
For example, with a modem configured for 8000 baud over the air, 9600baud serial ports, 2mS time-out, the total time for a MODBUS “Read Module Name” command ($01M) command to receive the response back is 150mS in Packet Mode.
A DF1 polling system with M5 Fireline or M7 modems configured for 8000 baud over the air, 9600baud serial ports, 2mS time-out, and Streaming Mode will allow RTU’s to be polled and responses returned in about 80mS round-trip.