SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
The DCAN module performs CAN protocol communication according to ISO 11898-1. The bit rate can be programmed to values up to 1 Mbit/s. Additional transceiver hardware is required for the connection to the physical layer (CAN bus).
For communication on a CAN network, individual message objects can be configured. The message objects and identifier masks are stored in the message RAM.
All functions concerning the handling of messages are implemented in the message handler. Those functions are acceptance filtering, the transfer of messages between the CAN core and the message RAM, and the handling of transmission requests, as well as the generation of interrupts or DMA requests.
The register set of the DCAN module can be accessed directly via the module interface. These registers are used to control and configure the CAN core and the message handler, and to access the message RAM.
Figure 24-169 shows the DCAN block diagram and its features are described below.
CAN Core: The CAN core consists of the CAN protocol controller and the Rx/Tx shift register. It handles all ISO 11898-1 protocol functions.
Message Handler: The message handler is a state machine that controls the data transfer between the single-ported message RAM and the CAN core’s Rx/Tx shift register. It also handles acceptance filtering and the interrupt/DMA request generation as programmed in the control registers.
Message RAM: The DCAN enables a storage of 64 CAN messages.
Message RAM Interface: Three interface register sets control the MPU read and write accesses to the message RAM. There are two interface registers sets for read and write access, IF1 and IF2, and one interface register set for read access only, IF3. Additional information can be found in Section 24.10.4.8.12, Reading From a FIFO Buffer.
The interface registers have the same word-length as the message RAM.
Registers and Message Object Access: Data consistency is ensured by indirect accesses to the message objects. During normal operation, all software and DMA accesses to the message RAM are done through interface registers. In a dedicated test mode, the message RAM is memory mapped and can be directly accessed by either MPU or DMA.
Module Interface: The DCAN module registers are accessed by the user software through a 32-bit peripheral bus interface.
Clocking: Two clocks are provided to the DCAN module: the peripheral synchronous clock (interface clock [ICLK]) and the peripheral asynchronous clock (functional clock [FCLK]) .