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Section 7. Installation
281
CR800 Serial Ports
Serial Port
Voltage Level
Logic
RS-232
(9 pin)
RS-232
Full-duplex asynchronous RS-
232
CS I/O
(9 pin)
TTL
Full-duplex asynchronous RS-
232
COM1
(
C1 – C2
)
TTL
Full-duplex asynchronous RS-
232/TTL
COM2
(
C3 – C4
)
TTL
Full-duplex asynchronous RS-
232/TTL
C1
5 VDC
SDI-12
C3
5 VDC
SDI-12
C1, C2, C3
5 VDC
SDM (used with Campbell
Scientific peripherals only)
7.7.17.3 Protocols
PakBus is the protocol native to the CR800 and transparently handles routine
point-to-point and network communications among PCs and Campbell Scientific
dataloggers. Modbus and DNP3 are industry-standard networking SCADA
protocols that optionally operate in the CR800 with minimal user configuration.
PakBus®, Modbus, and DNP3 operate on the
RS-232
,
CS I/O
, and four COM
ports. SDI-12 is a protocol used by some smart sensors that requires minimal
configuration on the CR800.
Read More
See
SDI-12 Sensor Support — Details
(p. 385),
PakBus
Comms — Overview
(p. 77),
DNP3 — Details
(p. 436),
and
Modbus — Details
(p. 436).
Many instruments require non-standard protocols to communicate with the
CR800.
Note
If an instrument or sensor optionally supports SDI-12, Modbus, or
DNP3, consider using these protocols before programming a custom
protocol. These higher-level protocols are standardized among many
manufacturers and are easy to use relative to a custom protocol. SDI-12,
Modbus, and DNP3 also support addressing systems that allow
multiplexing of several sensors on a single communication port, which
makes for more efficient use of resources.
7.7.17.4 Glossary of Serial I/O Terms
Term: asynchronous
The transmission of data between a transmitting and a receiving device
occurs as a series of zeros and ones. For the data to be "read" correctly, the
receiving device must begin reading at the proper point in the series. In
Summary of Contents for CR800 Series
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