Are you asking about NMEA-0183 serial data connections?
Or, are you asking about NMEA-2000 network data construction?
The two are quite different approaches to exchanging data between marine electronic devices.
If you are asking about NMEA-0183 serial data connections, please read my several articles about them:
The following are listed in the
REFERENCE section index, under the sub-heading of
NMEA-0183:
Guide to NMEA-0183 Interconnectionshttp://continuouswave.com/whaler/reference/guideNMEA0183.htmlUniversal NMEA-0183 Interfacehttp://continuouswave.com/whaler/reference/UniversalNMEA0183.htmland to help you interconnect various products, see my collection of information at
NMEA-0183 Interface Data Collectionhttp://continuouswave.com/forum/viewtopic.php?f=9&t=816Note the above article is pinned to the listing of articles in this forum's index.
If you are asking about NMEA-2000 network construction, read my extensive primer about NMEA-2000 networks which has been written for readers who have no prior knowledge of them. It has been available in the REFERENCE section listing. You can find it at
NMEA-2000 Networks and Modern Outboard Engineshttp://continuouswave.com/whaler/reference/NMEA2000.htmlThe primer also links to more than a dozen follow-on articles containing more information. Reading those additional articles will also be informative.