Serial Data Networking of Marine Electronic Devices


[Home]

NMEA 2000 Bus Description

The NMEA Standards Committee developed the NMEA 2000 interface which is based on the CAN Bus protocol as data link layer, and transceivers according to ISO 11898-2 as physical layer. The higher-layer protocol is based on J1939 and ISO 11783. The Controller Area Network (CAN) specification defines the Data Link Layer, ISO 11898 defines the Physical Layer.

The CAN bus [CANbus] is a Balanced (differential) 2-wire interface running over either a Shielded Twisted Pair (STP), Un-shielded Twisted Pair (UTP), or Ribbon cable. Each node uses a Male 9-pin D connector. The Bit Encoding used is: Non Return to Zero (NRZ) encoding (with bit-stuffing) for data communication on a differential two wire bus. The use of NRZ encoding ensures compact messages with a minimum number of transitions and high resilience to external disturbance.

CAN Bus Electrical Interface Circuit

One data rate is defined at 250kbps (Bits per second) being the top end, and 10kbps. Cable length depends on the data rate used, but may be 200 meters at the 250kbps data rate.

The CAN Bus interface uses an asynchronous transmission scheme controlled by start and stop bits at the beginning and end of each character. This interface is used, employing serial binary interchange. Information is passed from transmitters to receivers in a data frame. The data frame is composed of an Arbitration field, Control field, Data field, CRC field, ACK field. The frame begins with a 'Start of frame' [SOF], and ends with an 'End of frame' [EOF] space. The data field may be from 0 to 8 bits. The frame check sequence is derived from a Cyclic Redundancy Code (CRC); the coefficients are generated modulo-2: X15 + X14 + X10 + X8 + X7 + X4 + X3 + 1. CAN implements five error detection mechanisms; 3 at the message level and 2 at the bit level [Also incorporates error flags]. At the message level: Cyclic Redundancy Checks (CRC), Frame Checks, Acknowledgment Error Checks. At the bit level: Bit Monitoring, Bit Stuffing. The CANbus pinout is shown in the table below.

	Web www.interfacebus.com

The pinout for the 5-pin connector is shown in the table below.

{NMEA-2000 Index}

CAN Bus Standard Organizations

NMEA {National Marine Electronics Association}
CiA {CAN In Automation - International Users and Manufactures Group}
ISO {International Organization for Standardization}
All other Standard Organizations

{NMEA-2000 Index}

CAN Bus Interface ICs

CAN Bus uses a Drive Voltage: High; 2.75v to 4.5 volts, Low; 0.5 to 2.25 volts, Differential 1.5v to 3.0 volts

CAN Bus Interface IC Logic Transition Levels

Analog Devices, Inc. {Mixed-Signal-DSPs (ADSP-21992) with 160MIPS and On-Chip CAN V2.0b}

Atmel Corp.

Cast {CAN Core, Bus Controller ICs}

Dallas Semiconductor 'Maxim' {DS80C390 Dual CAN High-Speed Microprocessor, bus controller ICs}

freescale {33389/33388 low speed fault tolerant CAN transceiver}

Infineon {82C900 Stand-alone TwinCan Controller-TLE6250 CAN Transceiver IC Manufacturer}

Inicore Inc. {CAN IP Core IC Manufacturer}

Intel {CanBus Interface 82527 IC}

Linear Technology {CAN Transceiver IC Manufacturer}

Maxim Integrated Products {DS80C390 Dual CAN High-Speed Microprocessor, bus controller IC}

Melexis {CAN Bus Transceiver IC Manufacturer}

Microchip {MCP2510 Stand-alone CanBus Controller IC}

National Semiconductor {uP with CAN Interface}

NXP {8/16-bit CAN Bus 2.0 Controllers/Transceiver}

Renesas Technology Corp {Micro-Controller [uC] with CAN / LIN Interface}

STMicroelectronics {uP with CAN Interface}

TI {TMS320F241 with CANbus Interface-3.3v Line Transceiver ICs}

IC Manufacturers List {All other types} {This Site}

{Back to NMEA-2000 Index}

Engineering Design Key words: NMEA 2000, Marine, CANbus Data Interface, Controller Area Network, Local Area Network, LAN, Shielded twisted-pair Digital Data Interface, Protocol layer, Topology, Physical, Mechanical, Size, Description, Brief, ICs, Integrated Circuits, Devices, COTS, Cards, Vendors, Products, Manufacturers, Industrial Bus, Automation, 11898, Pin out, Series, Interface, Design, Controller, Area, Network, Noise, Vessel, Motor vehicle, CAN Bus.

Home
Distributors	Components	Equipment	Software	Standards	Buses	Design	Reference