C8051F50x-F51x
22.2. CAN Registers
CAN registers are classified as follows:
1. CAN Controller Protocol Registers: CAN control, interrupt, error control, bus status, test modes.
2. Message Object Interface Registers: Used to configure 32 Message Objects, send and receive data
to and from Message Objects. The CIP-51 MCU accesses the CAN message RAM via the Message
Object Interface Registers. Upon writing a message object number to an IF1 or IF2 Command Request
Register, the contents of the associated Interface Registers (IF1 or IF2) will be transferred to or from the
message object in CAN RAM.
3. Message Handler Registers: These read only registers are used to provide information to the CIP-51
MCU about the message objects (MSGVLD flags, Transmission Request Pending, New Data Flags)
and Interrupts Pending (which Message Objects have caused an interrupt or status interrupt condition).
For the registers other than CAN0CFG, refer to the Bosch CAN User’s Guide for information on the func-
tion and use of the CAN Control Protocol Registers.
22.2.1. CAN Controller Protocol Registers
The CAN Control Protocol Registers are used to configure the CAN controller, process interrupts, monitor
bus status, and place the controller in test modes.
The registers are: CAN Control Register (CAN0CN), CAN Clock Configuration (CAN0CFG), CAN Status
Register (CAN0STA), CAN Test Register (CAN0TST), Error Counter Register, Bit Timing Register, and the
Baud Rate Prescaler (BRP) Extension Register.
22.2.2. Message Object Interface Registers
There are two sets of Message Object Interface Registers used to configure the 32 Message Objects that
transmit and receive data to and from the CAN bus. Message objects can be configured for transmit or
receive, and are assigned arbitration message identifiers for acceptance filtering by all CAN nodes.
Message Objects are stored in Message RAM, and are accessed and configured using the Message
Object Interface Registers.
22.2.3. Message Handler Registers
The Message Handler Registers are read only registers. The message handler registers provide interrupt,
error, transmit/receive requests, and new data information.
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