Microchip logo
  • All
  • Products
  • Documents
  • Applications Notes

MOST NetServices

The NetServices Application Programming Interface (API) provides a software interface to the MOST network low level system services. MOST NetServices provides access to all data transportation mechanisms on a MOST network.

The MOST System Management Module, another component of the MOST NetServices library, handles system related tasks ‘above’ the MOST NetServices API and can be considered as the ‘middleware’ of a MOST System. It addresses network and system management tasks.


MOST NetServices is a library made up of several components. Since all services are available as parts of a library, they can be included as needed to speed up the development of a MOST application. Callback functions provide easy access to the functionality of the MOST NetServices. Software switches provide an easy way to enable and disable functionality as needed. This allows for a reduction in code size, as only needed code is compiled.

MOST NetServices are delivered as full ANSI C source code and can be adapted to meet specific requirements by using a configuration file. For all components, Microchip's Automotive Information Systems supplies application examples in full source code for Borland C++Builder. Using MOST NetServices shortens development time of MOST devices, while reducing cost, increasing flexibility and ensuring MOST compatibility.


  • Simplifies the development of MOST devices through a standardized interface
  • Highly portable ANSI C source code
  • Frees the application from the hardware layer of the MOST network
  • Ensures compatibility to the MOST Specification
  • Fast device development
  • A library approach allows for implementation of only those functions that are needed
  • Reduced development costs
  • Extensive error handling
  • Easy expansion and customization
  • Free example programs to aid in development

The table below explains the interaction of the hardware, software and specification versions:

NetworkNIC / INICMOST SpecificationMOST NetServicesMOST System Management Module
MOST25OS8104ARev 2.5V 1.10.xV 1.2.1
OS81050V 2.1.x
OS8 1060
OS81092Rev 3.0V 3.0.xV 2.0.1
OS81118Rev 3.0 or Rev 3.1V3.2.xV3.0.x

MOST NetServices Layer I

MOST NetServices Layer I is the foundation of MOST NetServices providing the application with access to all the transportation mechanisms of MOST networks. Configuration files allow Layer I to be adapted to different application and platform requirements.

All INIC circuits have a majority of NetServices Layer integrated on-chip. A wrapper is required in MOST NetServices V2/V3 to interface to the Layer I on-chip. This wrapper is included in all grades and components.


  • Kernel for initialization of basic services and control of basic processes
  • MOST Supervisory and Startup Functions
  • Control Message Service for receiving, transmitting and buffering of control messages
  • Remote Control Service for remote reading and writing of devices
  • Application Message Service for handling segmented messages
  • Synchronous Channel Allocation Service for channel allocation and de-allocation for streaming data and administration for routing streaming data to and from the MOST network
  • Transparent Channel Allocation Service for handling of non-synchronous data streams
  • Asynchronous Data Transmission Service for receiving, transmitting and buffering of packet data
  • MOST Transceiver Control Service for providing access to the relevant registers of the MOST network Interface Chip
  • Selectable MOST device driver interface for register-based or message-based interface to the MOST network Interface Chip
  • Error handling and notification

MOST NetServices Layer II

NetServices Layer II, in combination with MOST NetServices Layer I, forms the basic core of a MOST device. The NetBlock and FBlock Enhanced Testability, mandatory parts of every MOST device, are integrated into Layer II grade. The Command Interpreter and Address Handler provide full support for functional addressing, allowing the application to ignore physical addresses of other devices in the MOST network. The Notification Service simplifies the distribution of status messages whenever an internal device property changes. Configuration files allow Layer II grade to be adapted to different application and platform requirements.


  • Kernel for initialization of Layer II services and control of processes
  • MOST Command Interpreter for received message interpretation
  • MOST Supervisor Layer II for network supervision and initialization
  • Address Handler with a de-central device registry for symbolic addressing support with or without a central registry 
  • Complete Function Block NetBlock, a mandatory part of every MOST device
  • Complete Function Block ET (Enhanced Testability), a mandatory part of every MOST device
  • Network Master Shadow for tracking messages from the Network Master
  • Notification Service for providing an easy and automatic means of notifying other devices of internal states and property changes
  • Error handling and notification

MOST High Protocol Service

In addition to Layer I and Layer II of the MOST NetServices, the MOST High Protocol Service (MHP) provides an alternative transmission path for packet data transfer, including an additional security layer. It allows large data packets of up to 64 KBytes to be sent and received. An acknowledgment mechanism provides a security layer to ensure data integrity.

MOST High Protocol Service interfaces to the Control Message Service (V1.x only: CMS), as well as to the Asynchronous Data Transmission Service (V1.x: ADS; V2.x/V3.x: WADS). So transmission can be done either via control channel, or the asynchronous channel of a MOST network.

Note: The V2.x/V3.x of the MOST NetServices supports asynchronous data transmission only.

MOST High Protocol consists of a separate transmit and receive section, allowing for reduced code when only one section is needed by a device. The transmit and receive sections can also be combined to enable full duplex transmissions. Configuration files allow the MOST High Protocol Service to be adapted to different application and platform requirements.


  • Provides data integrity to packet transport on the MOST network
  • Unlimited number of simultaneous connections
  • Flexible segmentation and acknowledgement mechanism
  • Transmissions can be paused or aborted by sender or receiver
  • Notification of application with transmission status
  • Input buffer can be locked by the application
  • Debug interface
  • Callback function for getting information about the status of connections
  • Interface to basic transmission services including Control Message Service (CMS), Asynchronous Data Transmission Service (ADS) and alternative packet driver
  • Error handling and notification

Packetizer 4 MOST High Service

The Packetizer 4 MOST High Service (PMHS) provides an alternative transmission route for application messages. Sending application messages in a packet on the asynchronous data channel results in faster transmission speeds and reduces the load on the control channel. Packetizer 4 MOST High Service is the best solution for devices sending large application messages.


  • Allows for transmission of application messages using the MOST High Protocol Service instead of the Application Message Service
  • Increases transmission speed of messages
  • Decreases traffic on the control channel of the MOST network
  • Error handling and notification


All MOST NetServices versions follow the same basic structure as shown in the overview below. Please find descriptions of the layers with the tabs above. Ordering MOST NetServices means to identify the version and define the grade and license type.

Please find MOST Specifications at the MOST Cooperation web site