COM2002X (ARCNET) Protocol

The com2002x protocol supports communication over ARCNET using Contemporary Controls COM20020/COM20022 ARCNET cards.

Syntax

com2002x://hostname:port?option=value,... % Use ARCNET, sending all messages to node ID indicated by "port"
    

Description

The com2002x protocol supports communication over ARCNET using Contemporary Controls COM20020/COM20022 ARCNET cards. It is identified by using com2002x as the protocol name in a URI.

The hostname in the URI is ignored. However, to have a properly formed URI the hostname must be specified. It is best to specify the "remote" host or device with which communications is being performed as a reminder of what is connected to the ARCNET card.

The port in the URI determines the ARCNET node ID of the destination card to which all messages are sent.

Limitations

Performance

Note that the data rates listed in the COM20020/22 Null Stack driver manual may not always be achieved. At present, using the COM20022 clock prescaler value of 6 yields data rates of approximately 1.5Mbps. It is important to calculate the data transfer time required for your application and determine if it can be accomplished within a sampling instant of your controller. It may be necessary to operate your communication blocks within an asynchronous thread (using the supported blocking mode) in order to avoid delaying your controller.

QUARC Target Manager

The com2002x protocol cannot be used for communicating with the target (via a target URI) because the com2002x protocol does not allow multiple connections on the same port. Hence, qc_set_default_model_uri cannot be used to set a default com2002x protocol for models. Instead, the model URI must be specified explicitly in the Code Generation/Interface/MEX file arguments option of the Configuration Parameters of the model as well as the target URI.

Multiple client connections

The com2002x protocol will only accept a single client connection at a time on a given port. It does not support time-division multiplexing of multiple client connections over a single com2002x port because doing so would require adding a header to the information packets sent over the port. QUARC communication protocols never add extra information to the data sent over the communication channel in order to allow QUARC to communicate with user applications, sensors and other devices which would not support QUARC-specific data packets.

Installation Requirements

Driver

In order to use the qrt_com2002x protocol the Contemporary Controls COM20020/22 Null Stack driver for Windows 2000/XP must be installed. This software should accompany your Contemporary Controls ARCNET card or may be available online. The qrt_com2002x protocol was tested with the Contemporary Controls COM20020/22 Null Stack driver version 1.5. Later versions of the driver may work but are untested at present.

Options

nodeid

This is the node ID of the local ARCNET card that is being used for communications over the network. Values must be between 0 and 255 inclusive.

board

This is the board number in the PC. Values range from 1 to 4, and the default board number is 1.

rcvbroadcasts

This is a boolean option which indicates whether or not the local ARCNET card is able to receive broadcast messages. The default behavior is to allow broadcast messages to be received. Valid values for this option are "0", "n", or "no" to indicate false, and "1", "y", or "yes" to indicate true.

rcvall

This is a boolean option which, when true, allows all network traffic to be received by this ARCNET card. The default value is false, so that the ARCNET card does not allow all messages to be received. Valid values for this option are "0", "n", or "no" to indicate false, and "1", "y", or "yes" to indicate true.

clock

This option is used to set the clock prescaler of the com2002x card. This option is dependent on your card. Valid values range from 0 to 6 inclusive, and the default value is 0. Note that not all values can be used with all com2002x cards, and you should refer to the COM20020/22 Null Stack driver manual for further details.

Driver

The driver supporting the Contemporary Controls COM20020/22 ARCNET communications is called qrt_com2002x.

Targets

See Also

• Communications
• QUARC Communications Protocols
• Communications Using the C Language

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