Campbell Scientific CR1000KD CR800 and CR850 Measurement and Control Systems - Page 334
PakBus Overview
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Section 8. Operation 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 nonPakBus® 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. 334