RV-M7 Data Radio Modem Technical Manual

Electrical Inputs and Outputs Your browser may not support display of this image.

Data Radio Inputs and Outputs

    The front panel of the M7 modem has these features:

    1. RF connector
    2. Power LED
    3. Status LED (Receive data = green,  TX = red)
    4. 9-Pin Serial I/O connector
    5. DC Power Jack
    1. LEDs

    The status LED visually show the current status of the radio.

    Status LED (TX) This LED blinks red when the transmitter keys and is putting out RF power.  It blinks green upon the reception of data or RF carrier. 

    Power LED (PWR)   This LED does a short blink, once every two seconds, indicating to the user that the power to the modem is ON and the modem is working.  When the modem is in the command mode, this LED will blink on and off, once per second.

    1. DC Power

    DC power for the modem is connected to the 2-pin DC power input jack labeled DC IN.  Use the supplied cable to connect the DC power. The red wire is positive (+) and the black wire is negative (-).   Its connection is optional, as the user may alternately apply power to Pin 9 and ground to pin 5 of the 9-pin I/O connector.

    The M7 modem is supplied with a DC power cable, Raveon part number 1C738-1.  

    Note: The M7 has in internal 3-amp mini-fuse (automotive type) to protect it and its power source against reverse voltage and serious hardware failures.  In the event it is blown due to a reverse voltage, it may be replaced by removing the internal circuit board and unplugging the fuse.  This must be done by a qualified electronic technician using ESD precautions.  
    RS232/EIA232 Serial I/O Connector

    The RS232 9-pin serial I/O connector is a female 9-pin D-subminiature connector having the following pins configuration.  It is pinned out so that it may be plugged directly into a computer or PC’s 9-pin COM port. 

    DB 9 Modem Connector

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    Front-view of DB-9 connector on modem (female)

    Pin Name Dir Function Level / Specification
    1 CD out Carrier detect If enabled, indicates presence of carrier.  Logical 0 (+ voltage on RS-232) means carrier is present.  If disabled, it is asserted (0) whenever the modem is operational, and not in the configuration mode.  It will be a 1 when the modem is in the configuration mode.
    2 RxD out Receive data Data out of the modem.
    3 TxD in Transmit data Data into the modem.
    4 DTR in Data terminal ready Normally ignored by the M7 modem. May control the power-state of the modem in low-power mode if this feature is enabled.
    5 GND   Ground connection Signal and power ground
    6 DSR out Data Set Ready Normally is set to 0 when modem is powered on and running.  Modem sets to a 1 when in low-power mode.
    7 RTS in Request to send Used to stop/start the flow of data coming out of the modem TxD pin.  0 = OK to send, 1 = don’t send. Leave disconnected if not used.
    8 CTS out Clear to send Used to stop the flow of data going into the RxD pin from the device connected to the M7.  0 = OK to send, 1 = don’t send.  If the M7 cannot accept more data, it will negate this signal (set to a 1).
    9 Power In/out DC power (not Ring signal) User may supply the DC power to the modem on this pin. 

    Note:   RS-232 signals use positive and negative voltages to represent digital 1s and 0s.  A positive voltage is a 0, and a negative voltage is a digital 1.

    This pin-out allows it to be directly plugged into a computer’s 9-pin serial port using a conventional 9-pin RS-232 serial cable.  To connect it to a modem, or computer peripheral that has a serial port, you will need a “null-modem” cable.  See Appendix A for more information on wiring a null-modem cable.

    To configure the M7 modem for RS-232 operation, use the ATIO 0 command.  RS-232 is the default operation mode for the connector.  RS-485 is a factory option.  See the next section for details on the RS-485 option.  

    1. -WX weatherproof Version

    The –WX version of the product is functionally the same as the standard version, except it is IP65 rated for weather resistance.   It has special water-resistant connectors on it, and a sealed enclosure to keep moisture out of the unit. 

    DC InputsYour browser may not support display of this image.

    The DC Input connector is a Bulgin PX0412/03P

    The RS232 I/O connector is a Hirose HR30-6R-6P(71)

    The RF I/O connection is a TNC female.

    Power Cord

    The DC power cord uses a Bulgin connector, part number SA3349/1.

    DC Power Cord with Bulgin ConnectorYour browser may not support display of this image.

    1. RS232 serial cable for –WX version

    The RS232 serial cable uses at Hirose connector, part number HR30-6P-6S(71). 

    Serial CableYour browser may not support display of this image.

 

    1. Optional EIA-485/RS-485 Serial I/O

    RS-485 Connector Pin Out

    RS-485 is a two-wire connection, with the pair of wires transmitting and receiving data.  With the RS-485 enabled (ATIO 2 command), the 9-pin serial I/O connector on the front of the M7  is a female 9-p D-subminiature connector having the following pins configuration. 

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    Front-view of DB-9 connector on modem (female)

    Pin # Name Dir Function Level / Specification
    1   - Do not connect Do not connect this pin to anything.  
    2 B (-) I/O B Inverting RS-485 data in line
    3 Out - out Z Connect to pin 2
    4 A (+)  I/O A Non-inverting RS-485 data out line
    5 GND   Ground Connect to earth ground.
    6   - Do not connect Do not connect this pin to anything.  
    7 Out + out Y Connect to pin 4
    8        
    9 Vin In/Out DC Power DC Power in or out if unit is powered using DC in jack.
 

    The RS485 differential line consists of two pins, A and B.

    A TxD-/RxD- aka inverting pin which is negative (compared to B) when the line is idle.

    B TxD+/RxD+ aka non-inverting pin which is positive (compared to A) when the line is idle.

    Configuring

    To configure the M7 modem for RS-485 operation, use the ATIO x command.  ATIO 2 sets the serial port for standard RS-485, full duplex.  ATIO 3 sets the serial port for RS-485 simplex mode.  In most cases, RS-485 simplex is preferred (ATIO 3 ).   In simplex RS-485 mode, the M7’s serial data receiver is internally disabled whenever it sends a character out the serial port, so that it will not receive its own data.  For most application use the RS485 simplex mode, ATIO 3.   If you are using two M7 modems with RS485 on both  units, you must use the simplex RS485 mode instead of the duplex RS485 mode, or the modems will enter an infinite loop-back condition.

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    Raveon’s RS-485 I/O circuit uses 3.3V logic to drive the lines, and the RS485 pins are ESD protected to ±15kV and 7kV human body model.  Input current is less than 150uA.  Output current when not driving the line is less than 50uA.

    Bias and Termination Resistors

    RS-485 installations typically have a termination resistor across the A and B lines.   For low-speed operation (<57600 baud), this resistor is probably not necessary. If you wish to use a terminating resistor, a value of 150 ohms should work in most applications.

    These A/B pin names are all in use on various types of equipment.  The RS485 signaling specification states that signal A is the inverting or '-' pin and signal B is the non-inverting or '+' pin. The same naming is specified in the NMEA standards.

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    When an RS-485 network is in an idle state, all nodes are in listen (receive) mode. Under this condition there are no active drivers on the network. All drivers are tri-stated.  Without anything driving the network, the state of the A and B line is unknown. If the voltage level at the receiver's A and B inputs is less than ±200mV the logic level at the output of the receivers will be the value of the last bit received.  In order to maintain the proper idle voltage state, bias resistors must be applied to force the data lines to the idle condition. 

    M7 RS-485 receivers have built-in bias resistors, offering the network a true “1/8 unit load”.  In most allocations, these internal bias resistors are sufficient, and an external bias resistor is not required.

    Phoenix Contact/Tyco makes a convenient DB-9 to terminal-block connector, part number 2761839. 

    1. RS422/EIA-422 Serial I/O Connector

    RS-422 communications uses 4-wire differential signals. The RS422 9-pin serial I/O connector is a female 9-p D-subminiature connector having the following pins configuration. 

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    Front-view of DB-9 connector on modem (female)

    Pin # Name Dir Function Level / Specification
    1   - Do not connect Do not connect this pin to anything.  
    2 B (-) In B Inverting RS-485 data in line
    3 Out - out Z Inverting data out pin
    4 A (+)  in A Non-inverting RS-485 data in line
    5 GND   Ground Connect to earth ground.
    6   - Do not connect Do not connect this pin to anything.  
    7 Out + out Y No-inverting data out
    8        
    9 Vin In/Out DC Power DC Power in or out if unit is powered using DC in jack.

    Configuring for RS-422

    To configure the M7 modem for RS-422 operation, use the ATIO 4 command.  You must order the RS-422 option for this to work, and only M7 modems with Revision E or higher hardware will work in RS-422 mode.  The M7’s hardware is identical to the RS-485 version, with the exception of two internal loop-back resistors. 

    Raveon’s RS-422 I/O circuit uses 3.3V logic to drive the lines, and the RS422 pins are ESD protected to ±15kV and 7kV human body model. 

    RS-422 installations typically have a termination resistor across the In and the Out lines.   A value of 150 ohms should work in most applications.

    Bias and Termination Resistors

    M7 RS-422 receivers have built-in bias resistors, offering the network a true “1/8 unit load”.  In most allocations, these internal bias resistors are sufficient, and an external bias resistor is not required.

    Serial out data comes out pins 3 and 7.  Serial input data comes in via pins 4 and 8.  Connect pin 5 to earth ground.

    M7 RS-422 receivers have built-in bias resistors, offering the network a true “1/8 unit load”.  In most allocations, these internal bias resistors are sufficient, and an external bias resistor is not required. 

    1. Low Power Mode (LPM)

    The M7 modem, has the ability to be put into a low power mode (LPM).  In LPM the modem draws much less current from the DC input.  In LPM, the internal radio in the M7 is disabled, as well as certain current-consuming hardware circuits.  The ability of the M7 to go into LPM is set with a configuration bit, using the ATSM 1 command. ATSM 1 configures the M7 to monitor the DTR input line, and enter the LPM mode whenever DTR is negated.   If the DTR signal is asserted, the M7 modem will operate normally. 

    The ATSM 2 command forces the M7 modem into the low-power mode.  IN the Low Power mode, the M7’s radio circuits are off, but it will still respond to serial commands and it will still transmit characters over the air, albeit with some latency as it has to power-up the radio each time it wishes to transmit. 

    The ATSM 0 command returns the M7 modem into the normal-operating mode with the receiver and transmitter operational.

    The M7 can switch between LPM and normal mode using the DTR line, and it switches much faster than using the DC power supply.  The M7 takes about ½ of a second to power on when DC is applied, but can switch between normal and LPM in about 25milliseconds.

    The factory default value for the ATSM setting is 0.  When ATSM is a zero, the M7 will not ever enter the LPM mode, and the DTR input signal is ignored.

    DTR negated means it is a negative voltage.  A voltage less than zero volts applied to DTR will turn the M7 off by putting it into LPM. 

    To assert the DTR signal (turn the modem on), the DTR line must be high (> 3V).   DTR is an input to an RS-232 transceiver IC.  It is ESD protected, and is safe for voltages from –20V to +20V input.

 

 

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