NI XNET XNET Session Frame Properties

XNET Session Frame Properties

• Frame:Output Queue Update Frequency
• Frame:Skip N Cyclic Frames
• Frame:CAN:Start Time OffsetFrame:CAN:Start Time Offset
• Frame:CAN:Transmit Time
• Frame:LIN:Transmit N Corrupted Checksums
• Frame:SAE J1939:Address Filter

Frame:Output Queue Update Frequency

Data Type	Direction	Required?	Default
u32	Write Only	No	0

Property Class

XNET Session

Property ID

nxPropSessionSub_OutputQueueUpdateFreq

Description

Note  This property should usually not be changed and is provided for advanced users. The value is given in 6-byte packets. The maximum value is 0xFFFF bytes, which results in 10922 6-byte packets. Setting the property to 0 will use the internally defined update frequency.

The property determines how often the NI-XNET firmware notifies the NI-XNET driver of frames being consumed from the output queue. The default value is related to the queue size. Very large queues can cause updates to be delayed. This property can be used to make the updates more frequently.

Note  This property affects the active frame object in the session. Review the nxSetSubProperty function to learn more about setting a property on an active frame.

Frame:Skip N Cyclic Frames

Data Type	Direction	Required?	Default
u32	Write Only	No	0

Property Class

XNET Session

Property ID

nxPropSessionSub_SkipNCyclicFrames

Description

Note  Only CAN interfaces currently support this property. When set to a nonzero value, this property causes the next N cyclic frames to be skipped. When the frame's transmission time arrives and the skip count is nonzero, a frame value is dequeued (if this is not a single-point session), and the skip count is decremented, but the frame actually is not transmitted across the bus. When the skip count decrements to zero, subsequent cyclic transmissions resume. This property is valid only for output sessions and frames with cyclic timing (that is, not event-based frames).

This property is useful for testing of ECU behavior when a cyclic frame is expected, but is missing for N cycles.

Note  This property affects the active frame object in the session. Review the nxSetSubProperty function to learn more about setting a property on an active frame.

Frame:CAN:Transmit Time

Data Type	Direction	Required?	Default
double	Write Only	No	From Database

Property Class

XNET Session

Property ID

nxPropSessionSub_CANTxTime

Description

Use this property to change the frame's transmit time while the session is running. The transmit time is the amount of time that must elapse between subsequent transmissions of a cyclic frame. The default value of this property comes from the database (the XNET Frame CAN:Transmit Time property).

If you set this property while a frame object is currently started, the frame object is stopped, the cyclic rate updated, and then the frame object is restarted. Because of the stopping and starting, the frame's start time offset is re-evaluated.

Note  This property affects the active frame object in the session. Review the nxSetSubProperty function to learn more about setting a property on an active frame.

Note  The first time a queued frame object is started, the XNET frame's transmit time determines the object's default queue size. Changing this rate has no impact on the queue size. Depending on how you change the rate, the queue may not be sufficient to store data for an extended period of time. You can mitigate this by setting the session Queue Size property to provide sufficient storage for all rates you use. If you are using a single-point session, this is not relevant.

Frame:LIN:Transmit N Corrupted Checksums

Data Type	Direction	Required?	Default
u32	Write Only	No	0

Property Class

XNET Session

Property ID

nxPropSessionSub_LINTxNCorruptedChksums

Description

When set to a nonzero value, this property causes the next N number of checksums to be corrupted. The checksum is corrupted by negating the value calculated per the database; (EnhancedValue * -1) or (ClassicValue * -1). This property is valid only for output sessions. If the frame is transmitted in an unconditional or sporadic schedule slot, N is always decremented for each frame transmission. If the frame is transmitted in an event-triggered slot and a collision occurs, N is not decremented. In that case, N is decremented only when the collision resolving schedule is executed and the frame is successfully transmitted. If the frame is the only one to transmit in the event-triggered slot (no collision), N is decremented at event-triggered slot time.

This property is useful for testing ECU behavior when a corrupted checksum is transmitted.

Note  This property affects the active frame object in the session. Review the nxSetSubProperty function to learn more about setting a property on an active frame.

Frame:SAE J1939:Address Filter

Data Type	Direction	Required?	Default
string	Write Only	No	""

Property Class

XNET Session

Property ID

nxPropSessionSub_J1939_AddrFilter

Description

You can use this property in input sessions only. It defines a filter for the source address of the PGN transmitting node. You can use it when multiple nodes with different addresses are transmitting the same PGN.

If the filter is active, the session accepts only frames transmitted by a node with the defined address. All other frames with the same PGN but transmitted by other nodes are ignored.

The value is a string representing the decimal value of the address. If your address is given as an integer value, you must convert it to a string value (for example, with sprintf (s, "%d", value)).

To reset the filter, set the value to empty string (default).

Note  This property affects the active frame object in the session. Review the nxSetSubProperty function to learn more about setting a property on an active frame.