49 lines
1.8 KiB
ReStructuredText
49 lines
1.8 KiB
ReStructuredText
.. _can_isotp:
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ISO-TP Transport Protocol
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#########################
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.. contents::
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:local:
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:depth: 2
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Overview
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********
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ISO-TP is a transport protocol defined in the ISO-Standard ISO15765-2 Road
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vehicles - Diagnostic communication over Controller Area Network (DoCAN).
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Part2: Transport protocol and network layer services. As its name already
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implies, it is originally designed, and still used in road vehicle diagnostic
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over Controller Area Networks. Nevertheless, it's not limited to applications in
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road vehicles or the automotive domain.
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This transport protocol extends the limited payload data size for classical
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CAN (8 bytes) and CAN-FD (64 bytes) to theoretically four gigabytes.
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Additionally, it adds a flow control mechanism to influence the sender's
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behavior. ISO-TP segments packets into small fragments depending on the payload
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size of the CAN frame. The header of those segments is called Protocol Control
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Information (PCI).
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Packets smaller or equal to seven bytes on Classical CAN are called
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single-frames (SF). They don't need to fragment and do not have any flow-control.
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Packets larger than that are segmented into a first-frame (FF) and as many
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consecutive-frames as required. The FF contains information about the length of
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the entire payload data and additionally, the first few bytes of payload data.
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The receiving peer sends back a flow-control-frame (FC) to either deny,
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postpone, or accept the following consecutive frames.
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The FC also defines the conditions of sending, namely the block-size (BS) and
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the minimum separation time between frames (STmin). The block size defines how
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many CF the sender is allowed to send, before he has to wait for another FC.
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.. image:: can_isotp_sequence.svg
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:width: 20%
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:align: center
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:alt: ISO-TP Sequence
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API Reference
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*************
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.. doxygengroup:: can_isotp
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:project: Zephyr
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