> For the complete documentation index, see [llms.txt](https://docs.influxtechnology.com/support_guides/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.influxtechnology.com/support_guides/dialog-user-guide/appendix-2/can-definitions.md).
# CAN Definitions
1. **Single Frame (SF)** – Protocol for short messages, contained in one frame, includes a length descriptor.
* **Data Length (DL)** – Encoded at the beginning of the message, the PCI is not included in the data length calculation. DL high and DL low encodes the data length for long messages into twelve bits, allowing a message length of up to 4095 bytes.
2. **First Frame (FF)** – The procedure for starting a long message, therefore segmented into multiple frames. It is only generated once for each log message by the sender of the segmented transfer.
* **Data Length (DL)** – DL high and DL low encodes the data length for long messages into twelve bits, allowing a message length of up to 4095 bytes.
3. **Flow Control Frame (FC)** – Used in a long message to control the Consecutive Frame transmissions. Generated by the receiver of a long message, it responds to a First Frame or the Consecutive last Frame.
* **Flow Status (FS)** – Codes in the PCI of the Flow Control Frame instruct the Consecutive Frame transmission, with two possible values:
* **Clear to Send (CTS, 000B)** – Resume message transmission, BS max and ST min were taken into account by the sender on the reception of the Flow Control frame.
* **Wait (WT, 001B)** – Pause transmission and wait for a CTS FC frame. ECU will only accept, not generate.
* **Block Size (BS max)** – Designates the maximum number of Consecutive Frames accepted in a block (between two Flow Control frames.) Possible values:
* **0** – No other Flow Control frame is expected. Therefore, the sender can transmit the following Consecutive Frames with the ST min value.
* **Separation Time (St min)** – Specifies the minimum gap between the transmission of the Consecutive Frames only and not between the Flow Control frame and the next Consecutive Frame. Units are milliseconds.
4. **Consecutive Frame (CF)** – When sending segmented data in a long message, all frames containing the data are encoded as Consecutive Frames. Upon receiving Consecutive Frames, the receiver shall assemble the data bytes until the message is received.
* **Sequence Number (SN)** – Designated the Consecutive Frame number in the current block. It detects duplication or loss of Consecutive Frames from a long message.
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