CDA70 MODEM DESCRIPTION
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2.3.2. Modem component
The modem part converts digital bit flow from the microcomputer to the FFSK or GMSK
analogue modulation, which is brought to the transmitter of the radio data module. And vice
versa, it converts analogue signal from the receiver to digital bit flow to the microcomputer.
The modem part is designed on the basis of a CML integrated circuit.
2.3.3. Microcomputer
The base of the radio data modem controlling microcomputer is represented by a 32-bit
processor with 1 MB of RAM, 512 kB of FLASH ROM and real time clock circuit with a back-up
power supply.
On one side, the microcomputer is connected to the radio data module via the modem
component; on the side of user interface, it is connected to circuits generating signals within
the RS232, RS485, M-BUS or Ethernet standard levels. The microcomputer provides for
connection of up to four user interfaces. All ports are terminated by RJ45 connectors marked
PORT1, PORT2, PORT3 and ETH. All RS232 ports are protected against overvoltage
incoming via data cable. If a device with RS485 interface is to be connected, a level converter
suitable for the appropriate application can be connected to the serial port. Different converters
will be used in case of connection on a short distance or in case galvanic separation is
necessary. The modem's microcomputer can be set for necessary control of the converter
(RS485). To each interface, a device with different communication protocol can be connected -
i.e. the microcomputer can also work as a converter of protocols between individual serial
ports. The wide range of radio modem functions can be set via any of RS232 communication
ports. In addition, the microprocessor manages numerous functions of servicing
and installation purposes. Apart from other important information, the microcomputer memory
records data transmission statistics, strength of signals from individual radio modems,
statistics of communication on individual serial ports, power failures, voltage of backup power
source and temperature inside the radio data modem. See Service manual for description
of service functions.
Configuration of the CDA70 radio data modem is stored in the permanent FLASH ROM
memory. See the Configuration of radio modem chapter for description of its settings.
2.3.4. Inputs and outputs for telemetry
As an option, customers may wish to install inputs and outputs for data collection
and controlling of technological processes in the radio modem. These signals are then led
to an RJ45 connector marked I/O. Five signals are led to this connector. Each of them can be
used either as input or output. Input is analogue 0 to 5V or digital with adjustable threshold.
The output is an open collector able to switch up to 500 mA. Reading and control of I/O signals
is possible both via the radio data network and from any serial RS232 interface. Two radio
data modems can make up a simple technology control, where changes on one modem input
signals can control remote output signals of the other modem and vice versa.
For multi-purpose usage, we supply an interface between the I/O connector
and the technology providing configurable voltage and current inputs, inputs for resistance
measurement (thermometers, barometers etc.), binary inputs with optical isolation and relay
