LIN

This session is selected from the LabVIEW project or returned from XNET Create Session. The session mode must be Frame Input Stream, Frame Input Queued, or Frame Input Single-Point.

If number to read is positive (or 0), the data array size is no greater than this number.

If number to read is negative (typically -1), all available frame values are returned. If number to read is negative, you must use a timeout of 0.

This input is optional. The default value is -1.

If the session mode is Frame Input Single-Point, set number to read to either -1 or the number of frames in the sessions list. This ensures that XNET Read (Frame LIN) can return the current value of all session frames.

The timeout is a LabVIEW relative time, represented as 64-bit floating-point in units of seconds.

If timeout is positive, XNET Read (Frame LIN) waits for number to read frame values, then returns that number. If the values do not arrive prior to the timeout, an error is returned.

If timeout is negative, XNET Read (Frame LIN) waits indefinitely for number to read frame values.

If timeout is zero, XNET Read (Frame LIN) does not wait and immediately returns all available frame values up to the limit number to read specifies.

This input is optional. The default value is 0.0.

If the session mode is Frame Input Single-Point, you must leave timeout unwired (0.0). Because this mode reads the most recent value of each frame, timeout does not apply.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Default value: No error

Each array element corresponds to a frame the session receives.

For a Frame Input Single-Point session mode, the order of frames in the array corresponds to the order in the session list.

The elements of each cluster are specific to the LIN protocol.

For the Frame Input Stream session mode, LIN frames are read in their raw form, without interpretation of their elements using the database. For the Frame Input Single-point and Frame Input Queued session modes, information from the database is used to interpret the LIN frames for ease of use.

The following cluster description applies to session modes Frame Input Single-point and Frame Input Queued.

The identifier is a number from 0 to 63. This number identifies the content of the data contained within payload.

The location of this ID within the frame depends on the value of event slot?. If event slot? is false, this ID is taken from the frame's header. If event slot? is true, this ID is taken from the first payload byte. This ensures that the number identifies the payload, regardless of how it was scheduled.

Regardless of its location, this is the unprotected ID, without parity applied.

If the value is true, the frame was received within an event-triggered slot. If the value is false, the frame was received within an unconditional or sporadic slot.

When this value is true, event ID contains the ID from the frame’s header.

When event slot? is true, event ID is the ID from the frame’s header. The event ID is a number from 0 to 63. This is the unprotected ID, without parity applied.

When event slot? is false, this value does not apply (it is 0).

This value is true only when you enable echo of transmitted frames by setting the XNET Session Interface:Echo Transmit? property to True.

The timestamp uses the LabVIEW absolute timestamp type.

The array size indicates the received frame’s payload length. According to the LIN protocol, this payload is 0-8 bytes in length.

If the frame payload is used within an event-triggered schedule entry (slot), the first byte of payload is the identifier of the frame in its protected form (checksum applied). This is required by the LIN standard even if the frame transmits in an unconditional or sporadic slot. For this type of LIN frame, the actual data (for example, signal values) is limited to 7 bytes.

For example, assume that frame ID 5 is received in an unconditional slot and an event-triggered slot of ID 9. When you receive from the unconditional slot, identifier is 5, event slot? is false, event ID is 0, and the first payload byte contains 5 with checksum applied. When you receive from the event-triggered slot, identifier is 5, event slot? is true, event ID is 9, and the first payload byte contains 5 with checksum applied. Regardless of how the frame is received, you can use the identifier to determine the contents of the actual payload data contents in bytes 2-8.

The following cluster description applies to session mode Frame Input Stream.

The identifier is a number from 0 to 63.

If the schedule entry (slot) is unconditional or sporadic, this identifies the payload data (LIN frame). If the schedule entry is event triggered, this identifies the schedule entry itself, and the protected ID contained in the first payload byte identifies the payload.

The node produces this output according to standard error behavior.

Standard Error Behavior