Campbell Scientific CR800 and CR850 Measurement and Control Systems - Manual (Page 334)

Section 8. Operation
334
allows multiple PCs to communicate with the CR800 simultaneously when proper
telecommunications networks are installed.
Typically, the PC initiates telecommunications with the CR800 via datalogger
support software
(p. 547).
However, some applications require the CR800 to call
back the PC (initiate telecommunications). This feature is called Callback.
Special features exclusive to LoggerNet
(p. 547)
enable the PC to receive calls from
the CR800.
For example, if a fruit grower wants a frost alarm, the CR800 can contact him by
calling a PC, sending an email, text message, or page, or calling him with
synthesized-voice over telephone. Callback has been utilized in applications
including Ethernet, land-line telephone, digital cellular, and direct connection.
Callback via telephone is well documented in CRBasic Editor Help (search term
"callback"). For more information on other available Callback features, manuals
for various telecommunications hardware may discuss Callback options. Contact
a Campbell Scientific applications engineer for the latest information in Callback
applications.
Caution When using the ComME communications port with non-
PakBus® protocols, incoming characters can be corrupted by concurrent
use of the CS I/O for SDC communication. PakBus® communication uses
a low level protocol of a pause / finish / ready sequence to stop incoming
data while SDC occurs.
Non-PakBus ® communication includes PPP protocol, ModBus, DNP3, and
generic, CRBasic-driven use of CS I/O.
Though usually unnoticed, a short burst of SDC communication occurs at
power-up and other times when the datalogger is reset, such as when
compiling a program or changing settings that require recompiling. This
SDC activity is the datalogger querying the SDC to see if the external
keyboard / display is available.
When DevConfig and PakBus Graph retrieve settings, the CR800 queries
the SDC to determine what SDC devices are connected. Results of the
query can be seen in the DevConfig and PakBusGraph settings tables.
SDC queries occur whether or not an SDC device is attached.
8.5 PakBus Overview
Read More! This section is provided as a primer to PakBus ® communications.
More information is available in PakBus Networking Guide, available at
www.campbellsci.com.
The CR800 communicates with computers or other Campbell Scientific
dataloggers via PakBus
® . PakBus ® is a proprietary telecommunications protocol
similar in concept to IP (Internet protocol). PakBus ® allows compatible Campbell
Scientific dataloggers and telecommunications peripherals to seamlessly join a
PakBus
® network.