FlexCAN ModuleMPC5644A Microcontroller Reference Manual, Rev. 6Freescale Semiconductor 1393The module enters this mode when CR[LOM] is asserted. In this mode, transmission is disabled,all error counters are frozen and the module operates in a CAN Error Passive mode. Only messagesacknowledged by another CAN station will be received. If FlexCAN detects a message that has notbeen acknowledged, it will flag a BIT0 error (without changing the REC), as if it was trying toacknowledge the message.• Loop-Back Mode:The module enters this mode when CR[LPB] is asserted. In this mode, FlexCAN performs aninternal loop back that can be used for self test operation. The bit stream output of the transmitteris internally fed back to the receiver input. The Rx CAN input pin is ignored and the Tx CANoutput goes to the recessive state (logic ‘1’). FlexCAN behaves as it normally does whentransmitting and treats its own transmitted message as a message received from a remote node. Inthis mode, FlexCAN ignores the bit sent during the ACK slot in the CAN frame acknowledge fieldto ensure proper reception of its own message. Both transmit and receive interrupts are generated.• Module Disable Mode:This low power mode is entered when the MDIS bit in the MCR Register is asserted by the CPU.When disabled, the module sends a request to disable the clocks to the CAN Protocol Interface andMessage Buffer Management sub-modules. Exit from this mode is done by negating MCR[MDIS].See Section 32.5.9.2, Module Disable Mode, for more information.• Stop Mode:This low power mode is entered when Stop Mode is requested at MCU level. When in Stop Mode,the module puts itself in an inactive state and then informs the CPU that the clocks can be shutdown globally. Exit from this mode happens when the Stop Mode request is removed or whenactivity is detected on the CAN bus and the Self Wake Up mechanism is enabled. SeeSection 32.5.9.3, Stop Mode, for more information.32.3 External signal description32.3.1 OverviewThe FlexCAN module has two I/O signals connected to the external MCU pins. These signals aresummarized in Table 32-1 and described in more detail in the next subsections.Table 32-1. FlexCAN signalsSignal name11 The actual MCU pins may have different names.Direction DescriptionCAN_x_RX Input CAN receive pinCAN_x_TX Output CAN transmit pin
