CIP connection parameters

ctype

specifies the version of the connection parameter structure. For the current version of the RSLinx Classic SDK, the value in this field must always be DTL_CONN_CIP. Other values may be defined in future versions of the RSLinx Classic SDK to support expanded versions of the structure.

mode

specifies what events on the connection will cause the application's DTL_CIP_CONNECTION_STATUS_PROC and DTL_CIP_CONNECTION_PACKET_PROC callback functions to be called, as well as which functions can be used to send data on the connection. The value in this field should include one of:

The default mode is DTL_CIP_CONN_MODE_IS_SERVER. For transport classes 0 and 1, the 'client' receives data packets from the 'server'. For transport classes 2, 3, and 6, the 'client' sends data packets to the 'server', which returns responses. For transport classes 4 and 5, there is no difference between a 'client' and a 'server'. Both ends of the connection may send packets at will, and both ends are expected to return acknowledgments.

A data filter option may also be OR'ed into the

mode

field which will affect when the application's DTL_CIP_CONNECTION_PACKET_PROC callback function for the connection is called, if such a callback function was specified in a DTL_CIP_CONNECTION_OPEN (or DTL_CIP_LARGE_CONNECTION_OPEN) or DTL_CIP_CONNECTION_ACCEPT call. The choices are:

The default filter mode is DTL_CIP_MODE_FILTER_DUPLICATES. Note that regardless of the filter mode, a DTL_CIP_CONNECTION_PACKET_PROC callback function will only be called if there is actual data in a packet received on a connection. An acknowledgment packet without any data will never result in a DTL_CIP_CONNECTION_PACKET_PROC call.

There are several event notification options which may be OR'ed into the

mode

field (none of which are turned on by default) which will affect when the application's DTL_CIP_CONNECTION_STATUS_PROC callback function for the connection is called, if such a callback function was specified in the DTL_CIP_CONNECTION_OPEN (or DTL_CIP_LARGE_CONNECTION_OPEN) or DTL_CIP_CONNECTION_ACCEPT call. These options are:

trigger

specifies the circumstances under which new data should actually be sent across the connection.

Valid values are DTL_CIP_CONN_TRIGGER_CYCLIC, DTL_CIP_CONN_TRIGGER_CHANGE_OF_STATE, and DTL_CIP_CONN_TRIGGER_APPLICATION.

The value of

trigger

is only significant to the 'client' end of the connection. If the application is the 'client' (for example,

mode

= DTL_CIP_CONN_MODE_IS_CLIENT), then the

trigger

affects how RSLinx Classic uses the connection. If the application is requesting that the target be the 'client' (for example,

mode

= DTL_CIP_CONN_MODE_IS_SERVER), then the

trigger

affects how the target behaves. The

trigger

value is not significant for CIP transport classes 4 and 5.

transport

specifies the CIP transport class of the connection. Valid values are 0-6.

tmo_mult

specifies the multiplier applied to

OT.rpi

to obtain the connection timeout value (for example, how long RSLinx Classic will wait to receive a packet on the connection before closing the connection with a DTL_CONN_TIMEOUT status see [DTL_CIP_CONNECTION_STATUS_PROC]). The multiplier must be a value 0-7, interpreted according to the following table:

Value Multiplier

OT

and

TO

are, respectively, the network connection parameters for the originator-to-target network connection and the target-to-originator network connection:

conn_type

specifies the network connection type. Valid values are DTL_CIP_CONN_TYPE_POINT_TO_POINT, indicating a point-to-point connection, and DTL_CIP_CONN_TYPE_MULTICAST, indicating a multicast connection.

For this version of the RSLinx Classic SDK,

conn_type

must be set to DTL_CIP_CONN_TYPE_POINT_TO_POINT, indicating a point-to-point connection.

priority

specifies the priority of the network connection and must be one of the following:

DTL_CIP_PRIORITY_LOW Low priority connection

pkt_type

specifies whether data packets sent on this network connection are of fixed or variable length. Valid values are DTL_CIP_CONN_PACKET_SIZE_FIXED, indicating that all data packets must be exactly

pkt_size

bytes long, and DTL_CIP_CONN_PACKET_SIZE_VARIABLE, indicating that data packets may be of any length up to

pkt_size

bytes. For CIP Messaging,

pkt_type

should be set to DTL_CIP_CONN_PACKET_SIZE_VARIABLE.

pkt_size

is the maximum number of bytes that can be sent on this network connection in a single transfer. For fixed-size transfers, this is also the exact number of bytes that must be sent. For DTL_CIP _CONNECTION_OPEN service, the maximum size is 511 bytes, while for DTL_CIP_LARGE_CONNECTION_OPEN service, the maximum size is 65,535 bytes theoretically. But the actual sizes depend on the types of devices and the communication paths oriented to the target devices.

rpi

specifies the RPI (Requested Packet Interval) for this network connection in microseconds.

api

specifies the API (Actual Packet Interval) for this network connection in microseconds. When the application originates a connection (see DTL_CIP_CONNECTION_OPEN and DTL_CIP_LARGE_CONNECTION_OPEN), it does not need to specify values for the

api

fields of the

OT

and the

TO

structures. Once the connection is successfully established, the

api

fields of the

TO

and

OT

structures will contain API values obtained during connection establishment.