DS791 Datasheet, PDF (9/46 Pages) Xilinx, Inc – LogiCORE IP AXI Controller

LogiCORE IP AXI Controller Area Network (axi_can) (v1.03.a)
Configuration Mode
The CAN controller enters the Configuration mode when any of the following actions are performed, regardless of
the operation mode:
• Writing a '0' to the CEN bit in the SRR register.
• Writing a '1' to the SRST bit in the SRR register. The core enters the Configuration mode immediately following
the software reset.
• Driving a '0' on the S_AXI_ARESET_N input. The core continues to be in reset as long as S_AXI_ARESET_N is
'0'. The core enters Configuration mode after S_AXI_ARESET_N is negated to '1'.
The following describes the Configuration mode features.
• CAN controller loses synchronization with the CAN bus and drives a constant recessive bit on the bus line.
• ECR register is reset.
• ESR register is reset.
• BTR and BRPR registers can be modified.
• CONFIG bit in the Status Register is '1.'
• CAN controller does not receive any new messages.
• CAN controller does not transmit any messages. Messages in the TX FIFO and the TX high priority buffer are
kept pending. These packets are sent when normal operation is resumed.
• Reads from the RX FIFO can be performed.
• Writes to the TX FIFO and TX HPB can be performed.
• Interrupt Status Register bits ARBLST, TXOK, RXOK, RXOFLW, ERROR, BSOFF, SLP and WKUP are cleared.
• Interrupt Status Register bits RXNEMP, RXUFLW can be set due to read operations to the RX FIFO.
• Interrupt Status Register bits TXBFLL and TXFLL, and the Status Register bits TXBFLL and TXFLL, can be set
due to write operations to the TX HPB and TX FIFO, respectively.
• Interrupts are generated if the corresponding bits in the IER are '1.'
• All Configuration Registers are accessible.
When in Configuration mode, the CAN controller continues to stay in this mode until the CEN bit in the SRR
register is set to '1’. After the CEN bit is set to '1', the CAN controller waits for a sequence of 11 recessive bits before
exiting Configuration mode.
The CAN controller enters Normal, Loop Back, or Sleep modes from Configuration mode, depending on the
LBACK and SLEEP bits in the MSR Register.
Normal Mode
In Normal mode, the CAN controller participates in bus communication by transmitting and receiving messages.
From Normal mode, the CAN controller can enter either Configuration or Sleep modes.
For Normal mode, the CAN controller state transitions are as follows:
• Enters Configuration mode when any configuration condition is satisfied
• Enters Sleep mode when the SLEEP bit in the MSR is '1'
• Enters Normal mode from Configuration mode only when the LBACK and SLEEP bits in the MSR are '0' and
the CEN bit is '1'
• Enters Normal mode from Sleep mode when a wake-up condition occurs
DS791 June 22, 2011
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Product Specification