Airmar PB200 - Manual (Page 8)

PB200 WeatherStation User Manual revision 1.000
Proprietary and Confidential
2
2. NMEA 2000® Interface
The Airmar PB200 WeatherStation has a single NMEA 2000®-compliant network
interface, and is expected to be certified as a Class 1 Level B device. The PB200
transmits and receives standard and proprietary NMEA 2000® Parameter Groups via this
interface. Transmitted PGNs (Parameter Group Numbers) are described in section 2.4.
Received PGNs are described in section 2.5.
2.1. Terminology
The following terms related to the NMEA 2000® protocol appear on the detailed PGN
pages to follow.
PGN: Parameter Group Number. NMEA 2000® messages are organized into logical
collections of data called Parameter Groups. The NMEA assigns each Parameter Group a
unique Parameter Group Number, or PGN.
Single Frame: Yes = the Parameter Group has been designed to fit within the 8 bytes of
a single CAN frame. No = the Parameter Group is larger than 8 bytes, so must be
transmitted in multiple CAN frames using either NMEA 2000® Fast Packets, or (TBD)
ISO 11783 multi-packets, using the Data Transfer Transport Protocol (PGNs 60160 and
60416).
Priority: NMEA 2000® parameter groups are each assigned a priority value between 0
and 7, which is used to arbitrate between two devices attempting to transmit
simultaneously. 0 is the highest priority, and 7 is the lowest. The Priority field at the top
of each of the detailed specification pages shows three values separated by slashes (e.g.
6/Y/Y). The first value is the default priority, between 0 and 7, of the parameter group as
defined in the NMEA 2000® Standard. The second value is "Y" if the priority for this
parameter group may be changed using the Command Group Function PGN 126208, or
"N" if the priority may not be changed. The third value is "Y" if the priority is saved in
nonvolatile EEPROM memory within the PB200 and maintained upon cycling power, or
"N" if the priority reverts to the default value upon cycling power.
Update Rate: Some NMEA 2000® parameter groups are transmitted periodically by the
PB200. The Update Rate field at the top of each of the detailed specification pages
shows three values separated by slashes (e.g. 100 ms/Y/Y). The first value is the default
update rate for the parameter group, as defined in the NMEA 2000® Standard. If the
default behavior for the parameter group is not to transmit periodically, then this first
value will be 0 (zero). The second value is "Y" if the update rate for this parameter group
may be changed using the Transmission Interval field in the Request Group Function
PGN 126208, or "N" if the update rate may not be changed. The third value is "Y" if the
update rate is saved in nonvolatile EEPROM memory within the PB200 and maintained
upon cycling power, or "N" if the update rate reverts to the default value upon cycling
power.