The MIMIC mode allows two or more M7 data radio modems to “mimic” each other’s digital I/O.  When in the MIMIC mode, the M7 will periodically transmit its digital status.  The M7 will also continue to operate as a radio modem, sending/receiving data using pins 2&3 of the DB9, but the other I/O pins of the DB9 will be used for digital input/output. The MIMIC mode also has a fail-safe setting, so that in the event the radio link is broken, the receiving MIMIC radio will automatically set the MIMIC output to a pre-defined state.

Normally, the Serial I/O connector operates like an RS232 serial interface.  If the MIMIC mode is enabled, the operation of the radio is modified to transmit the digital status of the INPUT0 and INPUT1 pins across the radio link, and output their status on the OUT0 and OUT1 pins.

Optional MOSFET Driver

The M7 radio modem has an optional MOSFET output driver on the OUT0 output. (Only the OUT0,, not the OUT1 output).  If this option is installed, OUT0 will be pulled to ground to energize an external relay or lamp whenever OUT0 was supposed to go low.  So closing S1 on the sending station will cause OUT0 to go low, energizing the relay/lamp/led…

The MOSFET that drives OUT0 is a 2N7002 type device.  Do not connect a lamp/relay that draws more than 100mA to OUT0.  Also, if OUT0 is driving an inductive load, use a surge-protection diode such as a 1N4001 across the load to prevent high-voltage transients.

If the optional MOSFET driver is not installed, OUT0 will simply follow INPUT0 with RS232 signal levels.

MIMIC mode will work without the optional MOSFET, but if you want the M7 radio do drive one relay or medium-current device, then you must order the MOSFET option for OUT0 from the factory when the M7 is purchased.

MIMIC Hardware

There are two aspects to the MIMIC mode:

1. The transmitter that sends the status of its digital inputs.  This is enabled with the MIMIC X Y command.
2. The unit that receives the over-the-air MIMIC message, and sets its digital outputs to match the inputs of the sending station.  This function is enabled with the ATIO 1 command.  ATIO 1 configures the DB9 serial port to operate with RS232 signal levels, and use the digital control lines for digital I/O instead of RS232 flow control.  ATIO 0 turns off MIMIC reception ability, and the digital I/O pins will operate as flow control signals.

The goal of the MIMIC mode is quite simple: Flip a switch at one location, and have something at another location turn on or off.

Configuring an M7 for MIMIC mode

MIMIC transmissions are enabled with the MIMIC X Y command.   MIMIC 0 disables MIMIC mode and puts the unit in standard radio modem operation mode.  MIMIC X Y with X and Y being any positive number will enable the MIMIC feature. The MIMIC X Y command sets the unit to transmit a MIMIC over-the-air message every X seconds when INPUT0 is low, and to every Y seconds when INPUT0 is high.

For complete details on configuring an M7 for MIMIC mode, see application note AN161_MIMIC_M7.

MIMIC Command settings

If digital input INPUT0 is low, every X seconds, the M7 will automatically transmit the digital status of both the the INPUT0 and INPUT1 pins.  If INPUT0 is high, every Y seconds, the M7 will automatically transmit the digital status of the INPUT0 and INPUT1 pins. For example, MIMIC 2 60 configures the radio to send the state of INPUT0 and INPUT1 pins every 2 seconds if INPUT0 is low, and every minute if INPUT0 is high.

Radio addressing operates as it does in the standard mode.  When a unit receives a MIMIC transmission intended for its ID, it will set its OUT0 and OUT1 pins as determined by the sending stations INPUT 0 and INPUT1.

When the unit is in the Command mode, MIIC transmissions will not take place. The command mode is entered by sending +++ into the serial port.  See the M7 Technical Manual for information on how to configure the M7 using the built-in commands.

The MIMIC transmissions are the same over-the-air format as a standard data transmission from an M7 radio modem, except they contain no user-data, only digital I/O information.  An M7 radio modem configured as a repeater will repeat the MIMIC messages.

Failsafe Settings

To ensure failsafe operation, a FAILSAFE A B command sets the minimum message interval, and the default digital output state if an over-the-air MIMIC message is not received within the failsafe period.  A is the minimum period, and B is the ASCII hex value of the digital outputs if the failsafe interval passes and no MIMIC messages are receive.  B is also the power-on default value of the digital outputs.

For example, FAILSAFE 60 1 configures the unit to require a MIMIC message at least every minute. If one is not received within 60 seconds, OUT0 will go high (open drain), and OUT1 will go low (below ground).

It is recommended that the A value for the FAILSAFE command be about 2.5 times longer than the largest of the X and Y values of the MIMIC command.  This allows for one MIMIC message to be missed.  For example if MIMIC transmissions are set to MIMIC 2 60, a reasonable FAILSAFE A B setting would be a value of 150 for A. This will allow one MIMIC message to be missed and the FAILSAFE value not kick in. If more than two MIMIC messages did not get received, after 150 seconds, the M7 would revert to the failsafe values.

The MIMIC mode allows two or more M7 data radio modems to “mimic” each other’s digital I/O.  When in the MIMIC mode, the M7 will periodically transmit its digital status.  The M7 will also continue to operate as a radio modem, sending/receiving data using pins 2&3 of the DB9, but the other I/O pins of the DB9 will be used for digital input/output. The MIMIC mode also has a fail-safe setting, so that in the event the radio link is broken, the receiving MIMIC radio will automatically set the MIMIC output to a pre-defined state.

Normally, the Serial I/O connector operates like an RS232 serial interface.  If the MIMIC mode is enabled, the operation of the radio is modified to transmit the digital status of the INPUT0 and INPUT1 pins across the radio link, and output their status on the OUT0 and OUT1 pins.

There are two aspects to the MIMIC mode:

1. The transmitter that sends the status of its digital inputs.  This is enabled with the MIMIC X Y command.
2. The unit that receives the over-the-air MIMIC message, and sets its digital outputs to match the inputs of the sending station.  This function is enabled with the ATIO 1 command.  ATIO 1 configures the DB9 serial port to operate with RS232 signal levels, and use the digital control lines for digital I/O instead of RS232 flow control.  ATIO 0 turns off MIMIC reception ability, and the digital I/O pins will operate as flow control signals.

The goal of the MIMIC mode is quite simple: Flip a switch at one location, and have something at another location turn on or off.

The telemetry industry has standardized on a number of different protocols to use in these types of applications. Most protocols were based upon the assumption that the cabling between the monitoring station and the RTU/PLC is an RS-232 or RS-422 serial link.  The protocols commonly used on these serial links are MODBUS-RTU, MODBUS-ASCII, DF1, DNP-3, and IEC870. All of these protocols can operate using hard-wired connections.  Because the Raveon Radios  mimic a hard-wire (data-in equals data-out), in most cases, the protocols will also work using a wireless modem. 

M5 and M7 Modems with Modbus

Raveon  radio modems support Modbus-ASCII networks with no special configuration.  Modbus-ASCII was designed specifically to work well over wired and wireless modems, and uses 7-bit data.  All Raveon  modems support 7-bit data. 

Modbus-RTU uses 8-bit data. Some modems and older systems do not work with 8-bit data, but Raveon’s  wireless modems support both 7 bit and 8 bit data.  There are some considerations when using radio modems with Modbus-RTU:

Latency    The difference between M5 and M7 series wireless modems and a multi-drop wired network is that the wireless modems introduce some additional latency (delay) into the system.  Most Modbus-RTU applications can tolerate this latency, but some cannot.  If your Modbus application does not tolerate latency, then use Modbus –ASCII.  Modbus-ASCII is compatible with Raveon  radio modems. The following table shows Latency vs. Over-the-air bit rate for Raveon narrow band radio modems in the packetized mode. 

Time-Outs    Some versions of the Modbus protocol have short response timeout requirements that may not be compatible with radio modem latencies.   Modbus-RTU is compatible with the normal FireLine latencies but does have inter-character delay requirements that must be met. Raveon modems have programmable time-outs to facilitate the control of latency.

Modem IDs       The M5 and M7 series modems have 16 bit IDs.  Most SCADA systems work in a broadcast configuration, where all modems hear all other modems.  To do this, set the net mask to all zeors  (ATMK 0000).  Be sure to set each unit ID in each modem to a unique ID number, so that the duplicate packet filtering works properly.  All Raveon modems filter out duplicate packets, so that operation with repeaters does not cause duplicate packets being received.

For lowest latency, Raveon’s unique “Streaming” mode of operation provides data transfer with latency only slightly higher than wired configurations.  No other radio modem on the market offers both error-free packetized operation AND Streaming data operation.

M5 and M7 Modems with DF1

The DF1 protocol works well with the Raveon radio modems as long as the over-the-air data rate is set to 4800 bps or higher.  The stock-configuration of the radio modem works with the Rockwell  “DF1 Polling Driver”. 

To reduce latency in the polling, it is suggested that certain stock-parameters in the FireLine be a adjusted to values more optimized for use in a polled environment.  The following is a list of parameters in the radio that may be adjusted to reduce latency when using the DF1 protocol. 

1)   Reduce the serial-port time-out value down to 2mS (ATR3 2)

2)   Set the serial port to 19200bps  (ATBD 4)

3)   Configure the Over the air data rate to 8000bps (ATR2 4)  This will reduce the communication range, so only do this if the link-margin on the system is adequate.

Use the “Streaming Mode” of communications.  (ATMT 2)   The factory default is the “Packet Mode”, where all data is error checked and sent in packets.  The Streaming mode initiates transmissions faster, and sends characters over-the-air as they stream in, but does not check for errors.  DF1 is tolerant of noise and over-the-air bit errors, and in most cases works well in streaming mode.  In mission-critical or safety situations, packet mode would be more appropriate as it’s data transmission is more deterministic.

High-speed over the air data rates. 19200bps in 25kHz channel, 9600bps in 12.5kHz.

Remote status monitoring including DC voltage, packet error statistics, modem “up time”, and receiver signal strength. 

Easy to use. Plug-in, Turn-on, and GO.  Transmit data in = Receive data out.

Lowest current draw in industry.  The M5 wireless modems draw less than 110mA when fully operational, and the M7s less than 90mA. 

Wide input voltage with high-efficiency switching voltage regulator.

Packetized AND Streaming Data.  Integrated Packetized data protocol with error correction and built-in Streaming Real-Time operation. User selectable.

ARQ error correction and retransmission capability.  Totally transparent to the application.

Capable of store-and-forward repeating operation.

Small size.   Extruded aluminum enclosure is small, and very rugged.

16 bit addressing for up to 65,525 different unique device addresses per channel.  Radio channels may be shared with no interference between users.

Supports group and broadcast transmissions.  Network mask allows groups of any size.

Easily to configure.  Raveon  modems are configured using “AT” commands through the modem’s serial port.  Raveon also provides free of charge, Radio Manager, a easy-to-use PC program with a graphical user interface to configure and program all Raveon Radios.

RS-232, RS422, or RS485 serial port.  Programmable serial baud rates up to 57600 make the FireLine M5 and the M7 radio modem compatible with most every PLC, PC, and HMI device made.  

Programmable over-the-air data rates.   With the M5 and M7 radios, you  can choose how your system will work.  Set the OTA data slower for extended communication range, or set it fast for lowest latency.  Your choice.

SkyLine compatibility mode for use in older Sonik radio systems.