CR300-Series Datalogger
36
The CR300 can be programmed to act as an SDI-12 data recorder or as an SDI-
12 sensor. The
SDI12Recorder()
instruction automates sending commands
and recording responses. With this instruction, the commands to poll sensors
and retrieve data are done automatically with proper elapsed time between the
two. The CR300 automatically issues retries. See
CRBasic Editor Help
for
more information on this instruction.
CRBasic SDI-12 instructions include:
•
SDI12Recorder()
•
SDI12SensorSetup()
•
SDI12SensorResponse()
6.5.4 Modbus Communications
The CR300 supports Modbus RTU and Modbus ASCII protocols and can be
programmed as a Modbus master or Modbus slave. These protocols are often
used in Modbus SCADA networks. The CR300 communicates with Modbus
over RS-232. Ports
RS-232
and
Com1
can be configured for Modbus RS-232
communication.
Modbus has a set command structure. It uses a common bus and addresses each
node, so field instruments are effectively multiplexed to a CR300 without
additional hardware.
CRBasic Modbus instructions include:
•
ModbusMaster()
•
ModbusSlave()
•
MoveBytes()
See
CRBasic Editor Help
for the most recent information on each of these
instructions and for program examples.
6.5.5 DNP3 Communications
DNP3 (Distributed Network Protocol) is designed to optimize transmission of
data and control commands from a master computer to one or more remote
devices or outstations. Ports
RS-232
and
Com1
can be configured for DNP3
communication. See application note
, available at
, for detailed information and
program examples.
CRBasic DNP3 instructions include:
•
DNP()
•
DNPUpdate()
•
DNPVariable()
6.5.6 PakBus Communications
PakBus is a protocol similar in concept to IP (Internet Protocol). By using
signatured data packets, PakBus increases the number of communication and
networking options available to the CR300. Communication can occur via
TCP/IP, on the
USB
port, the
RS-232
port, and the
C
terminals.
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