Bosch Appliances TTCAN user manual Synchronisation on late and early Edges

Page 48

TTCAN

User’s Manual

Revision 1.6

When the phase error of the edge which causes Resynchronisation is negative, Phase_Seg2 is shortened. If the magnitude of the phase error is less than SJW, Phase_Seg2 is shortened by the magnitude of the phase error, else it is shortened by SJW.

When the magnitude of the phase error of the edge is less than or equal to the programmed value of SJW, the results of Hard Synchronisation and Resynchronisation are the same. If the magnitude of the phase error is larger than SJW, the Resynchronisation cannot compensate the phase error completely, an error of (phase error - SJW) remains.

Only one synchronisation may be done between two Sample Points. The synchronisations maintain a minimum distance between edges and Sample Points, giving the bus level time to stabilize and filtering out spikes that are shorter than (Prop_Seg + Phase_Seg1).

Apart from noise spikes, most synchronisations are caused by arbitration. All nodes synchronise “hard” on the edge transmitted by the “leading” transceiver that started transmitting first, but due to propagation delay times, they cannot become ideally synchronised. The “leading” transmitter does not necessarily win the arbitration, therefore the receivers have to synchronise themselves to different transmitters that subsequently “take the lead” and that are differently synchronised to the previously “leading” transmitter. The same happens at the acknowledge field, where the transmitter and some of the receivers will have to synchronise to that receiver that “takes the lead” in the transmission of the dominant acknowledge bit.

Synchronisations after the end of the arbitration will be caused by oscillator tolerance, when the differences in the oscillator’s clock periods of transmitter and receivers sum up during the time between Synchronisations (at most ten bits). These summarized differences may not be longer than the SJW, limiting the oscillator’s tolerance range.

The examples in figure 11 show how the Phase Buffer Segments are used to compensate for phase errors. There are three drawings of each two consecutive bit timings. The upper drawing shows the synchronisation on a “late” edge, the lower drawing shows the synchronisation on an “early” edge, and the middle drawing is the reference without synchronisation.

Rx-Input

 

 

“late” Edge

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Sample-Point

manual_about.fm

Sample-Point

recessive dominant

Sample-Point

Sample-Point

Sample-PointSample-Point

Rx-Input

“early” Edge

recessive dominant

Sync_Seg

Prop_Seg

Phase_Seg1

Phase_Seg2

Figure 11: Synchronisation on “late” and “early” Edges

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11.11.02

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Contents User’s Manual Robert Bosch GmbHCopyright Notice and Proprietary Information Functional Overview 2.2. Block Diagram Operating Modes Change ControlConventions Scope References Terms and Abbreviations Can Application Ttcan Configuration Ttcan Schedule InitialisationTtcan Message Handling List of FiguresChange Control Current Status Change HistoryConventions Helvetica boldTerm Meaning Functional Overview Cpuifc TtcanOperating Modes Software Initialisation Can Message TransferDisabled Automatic Retransmission Test ModeTest Register addresses 0x0B & 0x0A Ttcan =1 Loop Back Mode Loop Back combined with Silent ModeNo Message RAM Mode Software control of Pin CantxAddress Name Reset Value Hardware Reset Description Ttcan Register SummaryCCE DAREIE SIENo Error Status Register addresses 0x03Error Counter addresses 0x05 Status InterruptsBit Timing Register addresses 0x07 BRP Extension Register addresses 0x0D & 0x0C IFx Command Mask Registers Direction = WriteArb IFx Command Request Registers Direction = ReadControl ClrIntPndBusy Message NumberIFx Message Buffer Registers IFx Mask RegistersIFx Message Control Registers IFx Data a and Data B RegistersMessage Object in the Message Memory ID28-0 Msk28-0Xtd Dir26/77 11.11.02 Message Handler Registers Interrupt Register addresses 0x09Transmission Request Registers New Data RegistersInterrupt Pending Registers 2 IF1 Data B1 and B2 Registers for Trigger Memory Access Message Valid 1 RegisterTrigger Number TT Operation Mode Register addresses 0x29 TypeTimeMark At CycleCount mod MPr2-0Eecs RdlcTEW TT Interrupt Enable Register addresses 0x31 CCMBark AppWdLCEL GTEGTW SWERTO TT Error Level Register addresses 0x3F & 0x3E TT Cycle Count Register addresses 0x3D & 0x3CTUR Numerator Configuration Low Register addresses 0x57 TUR Denominator Configuration Register addresses 0x59 TUR Numerator Actual Registers addresses 0x5B & 0x5ATT StopWatch Register addresses 0x61 QCS QgtpEcal EgtfTMC DETECS SWSEPE TMG40/77 11.11.02 Internal can Message Handling Data Transfer Between IFx Registers and Message RAMTransmission of Messages in Event Driven can Communication StartAcceptance Filtering of Received Messages Reception of Data FrameReception of Remote Frame Storing Received Messages in Fifo BuffersReceive / Transmit Priority Configuration of the ModuleSync PropSeg PhaseSeg1 PhaseSeg2 1 Configuration of the Bit TimingBit Time and Bit Rate Canclk input Nominal can Bit TimePropagation Time Segment BRPPhase Buffer Segments and Synchronisation Synchronisation on late and early Edges Filtering of Short Dominant Spikes Oscillator Tolerance Range 1.5 Configuration of the can Protocol ControllerCalculation of the Bit Timing Parameters Example for Bit Timing at high Baudrate Example for Bit Timing at low Baudrate 2 Configuration of the Message Memory2.1 Configuration of a Transmit Object for Data Frames 2.2 Configuration of a Single Receive Object for Data Frames2.3 Configuration of a Fifo Buffer Can Communication Handling of InterruptsUpdating a Transmit Object Changing a Transmit Object Reading Received MessagesRequesting New Data for a Receive Object Reading from a Fifo BufferCPU Handling of a Fifo Buffer Interrupt Driven Ttcan Configuration Ttcan TimingTUR 510 125000 32.5 100/12 529/17Message Scheduling Trigger Memory 63/77 11.11.02 Message Objects Reference MessagePeriodic Transmit Message Event Driven Transmit Message Time SlavesPotential Time Masters Ttcan Message Handling Message Reception Message TransmissionPeriodic Messages Event Driven MessagesTtcan Gap Control StopwatchCycle Time and Global Time Synchronisation Ttcan Interrupt and Error Handling Previous RefMarkConfiguration Example Register Remark Rdlc & TEW & CCMType & Msg & CycleCode RTO , TM , L2 , TTMode3 74/77 11.11.02 Generic InterfaceCustomer Interface Timing of the Wait output signal Canclk CanwaitbBusy = ‘1’ Busy = ‘0’ Interrupt TimingEOF
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