Loop Back Mode | Bosch Appliances TTCAN specs

TTCAN

User’s Manual

Revision 1.6

manual_about.fm

2.3.4.4 Loop Back Mode

The CAN_Core can be set in Loop Back Mode by programming the Test Register bit LBack to one. In Loop Back Mode, the CAN_Core treats its own transmitted messages as received messages and stores them (if they pass acceptance ﬁltering) into a Receive Buffer. Figure 3 shows the connection of signals CAN_TX and CAN_RX to the CAN_Core in Loop Back Mode.

CAN_TX CAN_RX

TTCAN

• •

Tx Rx

CAN_Core

Figure 3: CAN_Core in Loop Back Mode

This mode is provided for hardware self-test functions. To be independent from external stimulation, the CAN_Core ignores acknowledge errors (recessive bit sampled in the acknowledge slot of a data/remote frame) in Loop Back Mode. In this mode the CAN_Core performs an internal feedback from its Tx output to its Rx input. The actual value of the CAN_RX input pin is disregarded by the CAN_Core. The transmitted messages can be monitored at the CAN_TX pin.

2.3.4.5 Loop Back combined with Silent Mode

It is also possible to combine Loop Back Mode and Silent Mode by programming bits LBack and Silent to one at the same time. This mode can be used for a “Hot Selftest”, meaning the TTCAN hardware can be tested without affecting a running CAN system connected to the pins CAN_TX and CAN_RX. In this mode the CAN_RX pin is disconnected from the CAN_Core and the CAN_TX pin is held recessive. Figure 4 shows the connection of signals CAN_TX and CAN_RX to the CAN_Core in case of the combination of Loop Back Mode with Silent Mode.

CAN_TX CAN_RX

TTCAN

=1

•	•
Tx	Rx

CAN_Core

Figure 4: CAN_Core in Loop Back combined with Silent Mode

BOSCH

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11.11.02

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Bosch Appliances TTCAN user manual Loop Back Mode, Loop Back combined with Silent Mode

Contents

Robert Bosch GmbH User’s Manual Copyright Notice and Proprietary Information Change Control Functional Overview 2.2. Block Diagram Operating ModesConventions Scope References Terms and Abbreviations Can Application Ttcan Schedule Initialisation Ttcan ConfigurationTtcan Message Handling List of Figures Change History Change Control Current StatusConventions Helvetica bold Term Meaning Functional Overview Ttcan Cpuifc Can Message Transfer Operating Modes Software Initialisation Test Mode Disabled Automatic RetransmissionTest Register addresses 0x0B & 0x0A Ttcan =1 Loop Back combined with Silent Mode Loop Back Mode Software control of Pin Cantx No Message RAM Mode Address Name Reset Value Ttcan Register Summary Hardware Reset Description DAR CCEEIE SIE Status Register addresses 0x03 No Error Status Interrupts Error Counter addresses 0x05Bit Timing Register addresses 0x07 BRP Extension Register addresses 0x0D & 0x0C Direction = Write IFx Command Mask RegistersArb Direction = Read IFx Command Request RegistersControl ClrIntPnd Message Number BusyIFx Message Buffer Registers IFx Mask Registers IFx Data a and Data B Registers IFx Message Control RegistersMessage Object in the Message Memory Msk28-0 ID28-0Xtd Dir 26/77 11.11.02 Interrupt Register addresses 0x09 Message Handler Registers New Data Registers Transmission Request RegistersInterrupt Pending Registers Message Valid 1 Register 2 IF1 Data B1 and B2 Registers for Trigger Memory AccessTrigger Number Type TT Operation Mode Register addresses 0x29TimeMark At CycleCount mod MPr2-0 Rdlc EecsTEW CCM TT Interrupt Enable Register addresses 0x31Bark AppWdL GTE CELGTW SWE RTO TT Cycle Count Register addresses 0x3D & 0x3C TT Error Level Register addresses 0x3F & 0x3ETUR Numerator Conﬁguration Low Register addresses 0x57 TUR Numerator Actual Registers addresses 0x5B & 0x5A TUR Denominator Conﬁguration Register addresses 0x59TT StopWatch Register addresses 0x61 Qgtp QCSEcal Egtf DET TMCECS SWS TMG EPE 40/77 11.11.02 Data Transfer Between IFx Registers and Message RAM Internal can Message Handling Start Transmission of Messages in Event Driven can Communication Reception of Data Frame Acceptance Filtering of Received MessagesReception of Remote Frame Storing Received Messages in Fifo Buffers Conﬁguration of the Module Receive / Transmit Priority 1 Conﬁguration of the Bit Timing Sync PropSeg PhaseSeg1 PhaseSeg2Bit Time and Bit Rate Canclk input Nominal can Bit Time BRP Propagation Time Segment Phase 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 Range Calculation 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 Frames 2.3 Conﬁguration of a Fifo Buffer Handling of Interrupts Can Communication Updating a Transmit Object Reading Received Messages Changing a Transmit ObjectRequesting New Data for a Receive Object Reading from a Fifo Buffer CPU Handling of a Fifo Buffer Interrupt Driven Ttcan Timing Ttcan Conﬁguration 510 125000 32.5 100/12 529/17 TURMessage Scheduling Trigger Memory 63/77 11.11.02 Reference Message Message ObjectsPeriodic Transmit Message Time Slaves Event Driven Transmit MessagePotential Time Masters Message Transmission Ttcan Message Handling Message ReceptionPeriodic Messages Event Driven Messages Stopwatch Ttcan Gap Control Cycle Time and Global Time Synchronisation Previous RefMark Ttcan Interrupt and Error Handling Conﬁguration Example Rdlc & TEW & CCM Register Remark Type & Msg & CycleCode RTO , TM , L2 , TTMode3 74/77 11.11.02 Interface GenericCustomer Interface Canclk Canwaitb Timing of the Wait output signalBusy = ‘1’ Busy = ‘0’ Interrupt Timing EOF