Bosch Appliances TTCAN user manual Updating a Transmit Object

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TTCAN

User’s Manual

Revision 1.6

manual_about.fm

The interrupt identifier IntId in the Interrupt Register indicates the cause of the interrupt. When no interrupt is pending, the register will hold the value zero. If the value of the Interrupt Register is different from zero, then there is an interrupt pending and, if IE is set, the interrupt line to the CPU is active. The interrupt line remains active until the Interrupt Register is back to value zero (the cause of the interrupt is reset) or until IE is reset.

The value 0x4000 or 0xC000 indicates that an interrupt is pending in the TT Interrupt Vector Register and is enabled in the TT Interrupt Enable Register.

The value 0x8000 or 0xC000 indicates that an interrupt is pending because the CAN Core has updated (not necessarily changed) the Status Register (Error Interrupt or Status Interrupt). This interrupt has the highest priority. The CPU can update (reset) the status bits RxOk, TxOk and LEC, but a write access of the CPU to the Status Register can never generate or reset an interrupt.

All other values indicate that the source of the interrupt is one of the Message Objects, IntId points to the pending message interrupt with the highest interrupt priority.

The CPU controls whether a change of the Status Register may cause an interrupt (bits EIE and SIE in the CAN Control Register) and whether the interrupt line becomes active when the Interrupt Register is different from zero (bit IE in the CAN Control Register). The Interrupt Register will be updated even when IE is reset.

The Last Error Code LEC in the Status Register allows the interrupt service routine to analyse the CAN bus errors. AckError e.g. indicates that no other node is active on the CAN bus.

The CPU has two possibilities to follow the source of a message interrupt. First it can follow the IntId in the Interrupt Register and second it can poll the Interrupt Pending Register (see section 3.4.4).

An interrupt service routine reading the message that is the source of the interrupt may read the message and reset the Message Object’s IntPnd at the same time (bit ClrIntPnd in the Command Mask Register). When IntPnd is cleared, the Interrupt Register will point to the next Message Object with a pending interrupt.

4.3.2 Updating a Transmit Object

The CPU may update the data bytes of a Transmit Object any time via the IFx Interface Registers, neither MsgVal nor TxRqst have to be reset before the update.

Even if only a part of the data bytes are to be updated, all four bytes of the corresponding IFx Data A Register or IFx Data B Register have to be valid before the content of that register is transferred to the Message Object. Either the CPU has to write all four bytes into the IFx Data Register or the Message Object is transferred to the IFx Data Register before the CPU writes the new data bytes.

When only the (eight) data bytes are updated, first 0x0087 is written to the Command Mask Register and then the number of the Message Object is written to the Command Request Register, concurrently updating the data bytes and setting TxRqst with NewDat.

To prevent the reset of TxRqst at the end of a transmission that may already be in progress while the data is updated, NewDat has to be set together with TxRqst in event driven CAN communication. For details see section 4.1.2.

When NewDat is set together with TxRqst, NewDat will be reset as soon as the new transmission has started.

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Contents Robert Bosch GmbH User’s ManualCopyright Notice and Proprietary Information Functional Overview 2.2. Block Diagram Operating Modes Change ControlConventions Scope References Terms and Abbreviations Can Application Ttcan Schedule Initialisation Ttcan ConfigurationTtcan Message Handling List of FiguresChange History Change Control Current StatusConventions Helvetica boldTerm Meaning Functional Overview Ttcan CpuifcCan Message Transfer Operating Modes Software InitialisationDisabled Automatic Retransmission Test ModeTest Register addresses 0x0B & 0x0A Ttcan =1 Loop Back combined with Silent Mode Loop Back ModeSoftware control of Pin Cantx No Message RAM ModeAddress Name Reset Value Ttcan Register Summary Hardware Reset DescriptionDAR CCEEIE SIEStatus Register addresses 0x03 No ErrorError Counter addresses 0x05 Status InterruptsBit Timing Register addresses 0x07 BRP Extension Register addresses 0x0D & 0x0C IFx Command Mask Registers Direction = WriteArb Direction = Read IFx Command Request RegistersControl ClrIntPndMessage Number BusyIFx Message Buffer Registers IFx Mask RegistersIFx Message Control Registers IFx Data a and Data B RegistersMessage Object in the Message Memory Msk28-0 ID28-0Xtd Dir26/77 11.11.02 Interrupt Register addresses 0x09 Message Handler RegistersTransmission Request Registers New Data RegistersInterrupt Pending Registers 2 IF1 Data B1 and B2 Registers for Trigger Memory Access Message Valid 1 RegisterTrigger Number Type TT Operation Mode Register addresses 0x29TimeMark At CycleCount mod MPr2-0Eecs RdlcTEW CCM TT Interrupt Enable Register addresses 0x31Bark AppWdLGTE CELGTW 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 Qgtp QCSEcal EgtfDET TMCECS SWSTMG EPE40/77 11.11.02 Data Transfer Between IFx Registers and Message RAM Internal can Message HandlingStart Transmission of Messages in Event Driven can CommunicationReception of Data Frame Acceptance Filtering of Received MessagesReception of Remote Frame Storing Received Messages in Fifo BuffersConfiguration of the Module Receive / Transmit Priority1 Configuration of the Bit Timing Sync PropSeg PhaseSeg1 PhaseSeg2Bit Time and Bit Rate Canclk input Nominal can Bit TimeBRP Propagation Time SegmentPhase Buffer Segments and Synchronisation Synchronisation on late and early Edges Filtering of Short Dominant Spikes 1.5 Configuration of the can Protocol Controller Oscillator Tolerance RangeCalculation of the Bit Timing Parameters Example for Bit Timing at high Baudrate 2 Configuration of the Message Memory Example for Bit Timing at low Baudrate 2.2 Configuration of a Single Receive Object for Data Frames 2.1 Configuration of a Transmit Object for Data Frames2.3 Configuration of a Fifo Buffer Handling of Interrupts Can CommunicationUpdating a Transmit Object Reading Received Messages Changing a Transmit ObjectRequesting New Data for a Receive Object Reading from a Fifo BufferCPU Handling of a Fifo Buffer Interrupt Driven Ttcan Timing Ttcan ConfigurationTUR 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 Message Transmission Ttcan Message Handling Message ReceptionPeriodic Messages Event Driven MessagesStopwatch Ttcan Gap ControlCycle Time and Global Time Synchronisation Previous RefMark Ttcan Interrupt and Error HandlingConfiguration Example Rdlc & TEW & CCM Register RemarkType & Msg & CycleCode RTO , TM , L2 , TTMode3 74/77 11.11.02 Generic InterfaceCustomer Interface Canclk Canwaitb Timing of the Wait output signalBusy = ‘1’ Busy = ‘0’ Interrupt TimingEOF
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