PDU Router (PduR)

The PDU Router routes I-PDUs between upper modules such as Com and DCM, communication interfaces, and transport protocols. In doing so, it only translates the I-PDU IDs along configured routing paths and does not modify the content [SWS_PduR_00160]. Its tasks include transmission, reception, TriggerTransmit, segmented TP transmissions, and gateways with optional FIFO buffering. Routing takes place exclusively in the PDUR_ONLINE state after successful PduR_Init [SWS_PduR_00328]. At runtime, routing path groups can be switched via PduR_EnableRouting and PduR_DisableRouting.

more ›

The PDU Router routes I-PDUs between upper modules such as Com and DCM, communication interfaces such as CanIf, FrIf, and LinIf, as well as transport protocols. In doing so, it does not modify the I-PDUs [SWS_PduR_00160] and routes only along configured routing paths [SWS_PduR_00162]. Its core capability is the translation of I-PDU IDs on the transmit path as well as on the confirmation and indication paths [SWS_PduR_00766]. The interfaces are generic; the placeholders <Up>, <Lo>, and <LoTp> result from the configuration PduRBswModules [SWS_PduR_00504].

Context diagram: PduR is located between upper modules and IF or TP modules; BswM switches path groups, errors are reported to the DET. Sources: [SWS_PduR_00504], SWS PDU Router p. 16

PduR only knows the states PDUR_UNINIT and PDUR_ONLINE [SWS_PduR_00324]. Routing takes place exclusively in PDUR_ONLINE [SWS_PduR_00328]. It transitions there through PduR_Init(ConfigPtr) [SWS_PduR_00334]. Prior to that, all functions except PduR_Init and PduR_GetVersionInfo report the error PDUR_E_UNINIT, provided error detection is enabled [SWS_PduR_00119].

State diagram: Power-up leads to PDUR_UNINIT; only an error-free PduR_Init leads to PDUR_ONLINE. Sources: [SWS_PduR_00325], [SWS_PduR_00326], SWS PDU Router Fig. 7.2 p. 53

During operation, PduR handles the following sequences:

• It forwards transmit requests to each interface destination [SWS_PduR_00625].
• It routes TriggerTransmit requests to the upper layer [SWS_PduR_00430].
• For TP multicast, it requests the same data per destination using TP_CONFPENDING or TP_DATARETRY [SWS_PduR_00631] [SWS_PduR_00632] and reports an aggregated confirmation [SWS_PduR_00765].
• As a gateway, it optionally buffers in a FIFO [SWS_PduR_00785]. It can forward TP I-PDUs on the fly to exactly one destination starting from a threshold [SWS_PduR_00317] [SWS_PduR_00708].

At runtime, PduR_EnableRouting and PduR_DisableRouting switch entire routing path groups [SWS_PduR_00615] [SWS_PduR_00617], typically controlled by the BswM. Calls on a disabled path terminate with E_NOT_OK [SWS_PduR_00717]. PduR reports development errors such as PDUR_E_PDU_ID_INVALID to the DET [SWS_PduR_00100]. It reports FIFO losses as PDUR_E_PDU_INSTANCES_LOST [SWS_PduR_00670]. Dedicated error handling on interface paths does not exist; return values are passed back to the source SWS PDU Router p. 46.

more ›

Role and system boundary: I-PDU routing between upper modules, interfaces, and transport protocols

The PDU Router (PduR) is the central routing entity of the classic communication stack. It accepts I-PDUs from a source module and transfers them unchanged and consistently to one or more destination modules [SWS_PduR_00160]. Routing takes place exclusively along the configured routing paths [SWS_PduR_00162]. A path is uniquely determined by two specifications: the source I-PDU ID from the PduR configuration and the destination I-PDU IDs from the configurations of the called destination modules [SWS_PduR_00161]. The core capability of the PduR is therefore the translation of I-PDU IDs. This applies to the transmit path as well as to the confirmation and indication paths [SWS_PduR_00766]. Each module chooses its handle IDs independently; the configuration links them via the "global" Pdu ECU Configuration Fig. 3.13 p. 192.

Modules such as Com and DCM are located above PduR. Communication interfaces such as CanIf, FrIf, and LinIf, as well as transport protocols such as CanTp, FrTp, and LinTp, are located below SWS PDU Router p. 24. The interfaces are defined generically. The placeholders <Up>, <Lo>, and <LoTp> are replaced via the module configuration referenced in PduRBswModules, and for CDDs via their apiServicePrefix [SWS_PduR_00504] SWS PDU Router Fig. 10.2 p. 95. If a lower module supports both TP and IF, the infixes Tp and If are added [SWS_PduR_00800].

Context diagram: PduR is located between upper modules and lower IF or TP modules; BswM switches routing path groups, errors are reported to the DET. Sources: [SWS_PduR_00504], [SWS_PduR_00615], [SWS_PduR_00119], SWS PDU Router p. 16

If PduRZeroCostOperation is set and all routing paths are pre-compile, neighboring modules may call each other directly [SWS_PduR_00287]. If at least one path is not pre-compile, the generator must report an error [SWS_PduR_00619] SWS PDU Router p. 56. The generator shall optimize away unused features, i.e., TP, IF, gateway, and FIFO [SWS_PduR_00764].

Lifecycle: from PDUR_UNINIT via PduR_Init to PDUR_ONLINE

PduR possesses exactly one state machine [SWS_PduR_00644]. It has the states PDUR_UNINIT and PDUR_ONLINE from PduR_StateType [SWS_PduR_00324] [SWS_PduR_00742]. After power-on, the module is in PDUR_UNINIT [SWS_PduR_00325]. After successful PduR_Init, it transitions to PDUR_ONLINE [SWS_PduR_00326]. Routing only takes place in PDUR_ONLINE [SWS_PduR_00328]; nothing is routed in PDUR_UNINIT [SWS_PduR_00330] SWS PDU Router Fig. 7.2 p. 53. An older diagram additionally shows a state PDUR_REDUCED after failed initialization SWS PDU Router (alt) p. 30. This state does not apply to R20-11, as there are only two states here.

State diagram: After power-up, PduR is in PDUR_UNINIT and does not route; it routes in PDUR_ONLINE only after error-free PduR_Init. Sources: [SWS_PduR_00325], [SWS_PduR_00326], [SWS_PduR_00119], [SWS_PduR_00100], SWS PDU Router Fig. 7.2 p. 53

PduR_Init(ConfigPtr) is synchronous and non-reentrant [SWS_PduR_00334]. The function performs three things:

• It releases all buffers [SWS_PduR_00645].
• It sets the configured default values of the transmit buffers [SWS_PduR_00308].
• It enables the routing path groups according to the enable-at-start parameter [SWS_PduR_00709]. Later versions name this parameter PduRIsEnabledAtInit SWS PDU Router p. 131.

Prior to initialization, all functions except PduR_Init and PduR_GetVersionInfo report the error PDUR_E_UNINIT, provided PduRDevErrorDetect is active [SWS_PduR_00119]. PduR_GetVersionInfo [SWS_PduR_00338] is enabled via PduRVersionInfoApi System Template p. 656.

The post-build data is located in PduR_PBConfigType and implemented in PduR_PBcfg.c [SWS_PduR_00241] [SWS_PduR_00743]. It is uniquely identified via PduRConfigurationId [SWS_PduR_00281]. PduR_GetConfigurationId [SWS_PduR_00341] [SWS_PduR_00280] provides this identifier as an uint16-based PduR_PBConfigIdType; an ECU can contain multiple selectable configurations [SWS_PduR_00771]. Routing tables can be updated at post-build time [SWS_PduR_00295], though only in the uninitialized state [SWS_PduR_00296]. Memory consumption can grow with a new configuration and must therefore be planned for at design time SWS PDU Router p. 160.

Communication interface paths: Transmit, TriggerTransmit, and confirmations

If an upper module calls PduR_<User:Up>Transmit [SWS_PduR_00406], PduR calls <Lo>_Transmit for each destination [SWS_PduR_00625]. In doing so, it does not buffer [SWS_PduR_00629]. For the return value, the following applies:

• For singlecast, the return value is passed through unchanged [SWS_PduR_00432] [SWS_PduR_00626].
• In case of multicast, one successful destination is sufficient for E_OK [SWS_PduR_00218].

The destinations of a multicast are either all interfaces or all transport protocols, never mixed [SWS_PduR_00633].

CanIf copies the data directly upon Transmit SWS PDU Router Fig. 9.5 p. 100. FrIf and LinIf, in contrast, retrieve it later via PduR_<User:Lo>TriggerTransmit [SWS_PduR_00369]. PduR forwards this call to <Up>_TriggerTransmit [SWS_PduR_00430] and returns its return value [SWS_PduR_00661] SWS PDU Router Fig. 9.6 p. 101. PduR_<User:Lo>TxConfirmation [SWS_PduR_00365] is forwarded to <Up>_TxConfirmation together with the result [SWS_PduR_00627]. For multicast, this occurs only after the last confirmation [SWS_PduR_00589].

Sequence diagram: Transmission from Com with direct data provision (CanIf) or with delayed data retrieval via TriggerTransmit (FrIf), each with subsequent confirmation. Sources: [SWS_PduR_00625], [SWS_PduR_00430], [SWS_PduR_00627], SWS PDU Router Fig. 9.5 p. 100, SWS PDU Router Fig. 9.6 p. 101

Upon reception, PduR_<User:Lo>RxIndication [SWS_PduR_00362] leads to a call of <Up>_RxIndication for each upper destination [SWS_PduR_00621]; 1:n is supported [SWS_PduR_00164] SWS PDU Router Fig. 9.1 p. 97. PduR checks the length neither during local reception [SWS_PduR_00744] nor during local transmission [SWS_PduR_00745].

Transport protocol paths: segmented I-PDUs between DCM and TP modules

For TP transmission, PduR calls <LoTp>_Transmit for each destination [SWS_PduR_00634]. The TP module retrieves the data segment by segment via PduR_<User:LoTp>CopyTxData [SWS_PduR_00518]. PduR forwards each request to <Up>_CopyTxData [SWS_PduR_00299] and passes through the return value [SWS_PduR_00676] SWS PDU Router Fig. 9.9 p. 104.

For multicast, the upper layer must provide the same data multiple times. The request of the first destination is sent to the upper layer with TP_CONFPENDING [SWS_PduR_00631], all further requests with TP_DATARETRY [SWS_PduR_00632]. After the last confirmation, the upper layer receives a single <Up>_TpTxConfirmation. This reports E_OK if at least one destination reported E_OK [SWS_PduR_00765] SWS PDU Router Fig. 9.10 p. 83.

Sequence diagram: For TP multicast from DCM, PduR requests the same data per destination using TP_CONFPENDING or TP_DATARETRY and aggregates the confirmations. Sources: [SWS_PduR_00634], [SWS_PduR_00631], [SWS_PduR_00632], [SWS_PduR_00765], SWS PDU Router Fig. 9.10 p. 83

TP reception begins with PduR_<User:LoTp>StartOfReception [SWS_PduR_00507]. PduR forwards it to <Up>_StartOfReception [SWS_PduR_00549] and returns its return value unchanged [SWS_PduR_00623]. This is followed by two forwardings:

• CopyRxData [SWS_PduR_00512] is forwarded to <Up>_CopyRxData [SWS_PduR_00428].
• RxIndication [SWS_PduR_00375] is forwarded to <Up>_TpRxIndication [SWS_PduR_00429].

A call with SduLength 0 queries the available buffer or the available data [SWS_PduR_00740] SWS PDU Router Fig. 9.4 p. 99. PduR passes cancellations on to each destination. PduR_<User:Up>CancelTransmit results in <Lo>_CancelTransmit or <LoTp>_CancelTransmit [SWS_PduR_00769] [SWS_PduR_00723] [SWS_PduR_00724]. PduR_<User:Up>CancelReceive results in <LoTp>_CancelReceive [SWS_PduR_00727].

Sequence diagram: During TP reception from CanTp to DCM, PduR passes through StartOfReception, the CopyRxData loop, and RxIndication 1:1. Sources: [SWS_PduR_00549], [SWS_PduR_00428], [SWS_PduR_00429], SWS PDU Router Fig. 9.4 p. 99

Gateway operation: immediate forwarding, FIFO buffering, and on-the-fly TP

Between communication interfaces, PduR routes 1:n [SWS_PduR_00436] and with immediate forwarding, i.e., without its own rate control [SWS_PduR_00437]. Gatewaying is only performed IF↔IF or TP↔TP [SWS_PduR_00638]. For the forwarded length, the following applies:

• Without buffering, PduR forwards the minimum of the received length and the configured destination length [SWS_PduR_00783].
• With buffering, it copies at most PduRPduMaxLength and discards the remainder [SWS_PduR_00746].

An I-PDU can be routed locally to Com and simultaneously forwarded to a second CAN SWS PDU Router Fig. 9.14 p. 114.

How the destination obtains the data is determined by PduRDestPduDataProvision:

• With PDUR_DIRECT, the destination itself copies the data upon transmit [SWS_PduR_00303].
• With PDUR_TRIGGERTRANSMIT, PduR buffers and waits for TriggerTransmit [SWS_PduR_00306] SWS PDU Router Fig. 9.13 p. 108.

A FIFO can be configured per destination I-PDU [SWS_PduR_00307]. FIFO behavior applies for PduRQueueDepth greater than 1 [SWS_PduR_00785]. The activity diagram summarizes the input and output rules [SWS_PduR_00665] [SWS_PduR_00666].

Activity diagram: Depending on data provision and FIFO fill level, a gatewayed I-PDU is transmitted immediately, queued, or restarted after an overflow; TriggerTransmit and TxConfirmation empty the FIFO. Sources: [SWS_PduR_00665], [SWS_PduR_00793], [SWS_PduR_00786], [SWS_PduR_00787], [SWS_PduR_00255], [SWS_PduR_00669], [SWS_PduR_00666], [SWS_PduR_00667], [SWS_PduR_00662]

Two procedures exist for TP gateways. In direct gatewaying, <DstLoTp>_Transmit starts in the RxIndication with E_OK [SWS_PduR_00551]. In on-the-fly gatewaying, retransmission starts as soon as PduRTpThreshold is reached [SWS_PduR_00317]. In that case, only one destination is permitted [SWS_PduR_00708], and data already transmitted is not retransmitted [SWS_PduR_00707] SWS PDU Router p. 58. PduR selects the buffer by size:

• If the message fits into PduRPduMaxLength, it uses the dedicated buffer [SWS_PduR_00797].
• Otherwise, it dynamically retrieves a buffer from PduRTxBuffer [SWS_PduR_00798].

With TxConfirmation, it releases the buffer [SWS_PduR_00637]. If the I-PDU is additionally to be received locally, PduR calls <UpTp>_StartOfReception, <UpTp>_CopyRxData, and <UpTp>_RxIndication in this order [SWS_PduR_00789]. For this, it must buffer because DCM has no knowledge of the gateway SWS PDU Router p. 112.

Sequence diagram: In on-the-fly gatewaying between two CAN networks, forwarding begins as soon as the threshold is reached; reception and transmission run interleaved. Sources: [SWS_PduR_00317], [SWS_PduR_00708], [SWS_PduR_00797], [SWS_PduR_00799], [SWS_PduR_00637], SWS PDU Router Fig. 9.15 p. 110

Routing path groups: switching routing at runtime

Routing path groups bundle paths per network or PDU type. They are typically switched by BswM SWS PDU Router p. 69. PduR_EnableRouting(id) [SWS_PduR_00615] and PduR_DisableRouting(id, initialize) [SWS_PduR_00617] serve this purpose; the identifier is of type uint16 [SWS_PduR_00654]. The activation takes effect immediately [SWS_PduR_00715]. When disabling, the following rules apply:

• initialize decides whether single buffers are reset to the default value [SWS_PduR_00617].
• FIFOs of the stopped paths are cleared, and PduR reports PDUR_E_PDU_INSTANCES_LOST [SWS_PduR_00663].
• APIs called with the I-PDU ID of a disabled path return E_NOT_OK without further action [SWS_PduR_00717] [SWS_PduR_00710] [SWS_PduR_00726].

Later versions explicitly enumerate the affected functions SWS PDU Router p. 69.

Activity diagram: For an unknown group ID, the call returns without action (optionally with a DET report); otherwise, the group is immediately enabled or disabled, with FIFO flushing and buffer handling. Sources: [SWS_PduR_00647], [SWS_PduR_00648], [SWS_PduR_00716], [SWS_PduR_00649], [SWS_PduR_00715], [SWS_PduR_00663], [SWS_PduR_00717]

The Mode Management Guide recommends path groups for I-PDUs without a Com I-PDU group, such as for LdCom. Switching is performed via BswM rules, for example depending on the partial network state Mode Management Guide p. 50. The BswM action BswMPduRouterControl calls PduR_EnableRouting or PduR_DisableRouting for this purpose SWS BSW Mode Manager p. 145. In n:1 routing to a local module, at most one path may be active at runtime System Template p. 736 [SWS_PduR_00615].

Behavior in the event of an error

Development errors are defined by [SWS_PduR_00100]. They are reported only if PduRDevErrorDetect is active [SWS_PduR_00119] [SWS_PduR_00221]. PduR does not report production errors SWS PDU Router p. 60.

Error code	Value	Trigger
PDUR_E_INIT_FAILED	0x00	invalid configuration pointer
PDUR_E_UNINIT	0x01	API before initialization or PduR_Init outside of PDUR_UNINIT
PDUR_E_PDU_ID_INVALID	0x02	invalid PDU identifier
PDUR_E_ROUTING_PATH_GROUP_ID_INVALID	0x08	unknown group upon enable/disable [SWS_PduR_00648] [SWS_PduR_00649]
PDUR_E_PARAM_POINTER	0x09	null pointer as argument

The runtime error PDUR_E_PDU_INSTANCES_LOST occurs in three cases:

• A full FIFO is flushed upon the next reception [SWS_PduR_00255] [SWS_PduR_00670].
• <DstLo>_Transmit returns E_NOT_OK on a FIFO path. The entry is then removed and the next one is transmitted [SWS_PduR_00788] [SWS_PduR_00807].
• A path with FIFO is stopped [SWS_PduR_00663].

As a mandatory interface for this, PduR uses Det_ReportRuntimeError [SWS_PduR_91001].

On IF paths, PduR does not handle errors itself. It passes return values through to the source [SWS_PduR_00626] SWS PDU Router p. 46 and does not retry transmission [SWS_PduR_00256]. On TP paths as well, errors are passed to the upper layer via return value [SWS_PduR_00700] SWS PDU Router p. 49. With multiple destinations, E_OK applies only if all destinations return E_OK [SWS_PduR_00701]. This rule likely refers to TP multicast, whereas [SWS_PduR_00218] applies to IF multicast. Question Q-4bd42fd8dc77ccf2 (open) PduR merely forwards erroneous TP RxIndications [SWS_PduR_00207].

Dedicated rules apply to TP gateways:

• If RxIndication does not report E_OK, PduR stops processing [SWS_PduR_00689].
• If buffer space is lacking in the on-the-fly gateway, it returns BUFREQ_E_NOT_OK and aborts [SWS_PduR_00687].
• If no buffer is available at all, it returns BUFREQ_E_OVFL [SWS_PduR_00799].
• If one destination fails, the remaining destinations continue [SWS_PduR_00803]. If all fail, it stops the receive side [SWS_PduR_00804].
• If local reception fails, it terminates the session with the upper layer [SWS_PduR_00790] or reports E_NOT_OK via RxIndication [SWS_PduR_00791] [SWS_PduR_00792].

Further detailed evidence

The following references substantiate the statements in this guide. The sequences in Chapter 9 of the specification illustrate them, such as SWS PDU Router Fig. 9.5 p. 100.

• State model and routing enable: [SWS_PduR_00324], [SWS_PduR_00328].
• Initialization: [SWS_PduR_00334], [SWS_PduR_00645], [SWS_PduR_00709].
• Path identification and ID translation: [SWS_PduR_00161], [SWS_PduR_00766].
• IF paths: [SWS_PduR_00625], [SWS_PduR_00627], [SWS_PduR_00430].
• TP multicast: [SWS_PduR_00631], [SWS_PduR_00632], [SWS_PduR_00765].
• Gateway buffers and FIFO: [SWS_PduR_00306], [SWS_PduR_00785], [SWS_PduR_00665].
• Routing path groups: [SWS_PduR_00615], [SWS_PduR_00617], [SWS_PduR_00717]; usage with BswM: Mode Management Guide p. 50.
• Error codes: [SWS_PduR_00100], SWS PDU Router p. 72.