bosch_can_user guide 1/10 - 2. Functional Description

2. Functional Description

2.1 Functional Overview

The C_CAN is a CAN module that can be integrated as stand-alone device or as part of an ASIC. It is described in VHDL on RTL level, prepared for synthesis. It consists of the
components (see figure 1) CAN Core, Message RAM, Message Handler, Control Registers, and Module Interface.
The CAN_Core performs communication according to the CAN protocol version 2.0 part A and B. The bit rate can be programmed to values up to 1MBit/s depending on the used technology. For the connection to the physical layer additional transceiver hardware is required.
For communication on a CAN network, individual Message Objects are configured. The
Message Objects and Identifier Masks for acceptance filtering of received messages are
stored in the Message RAM.
All functions concerning the handling of messages are implemented in the Message Handler.
Those functions are the 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 the module interrupt.
The register set of the C_CAN can be accessed directly by an external CPU via the module interface. These registers are used to control/configure the CAN Core and the Message Handler and to access the Message RAM.
The Module Interfaces delivered with the C_CAN module can easily be replaced by a
customized module interface adapted to the needs of the user.

The C_CAN implements the following features:
• Supports CAN protocol version 2.0 part A and B
• Bit rates up to 1 MBit/s
• 32 Message Objects
• Each Message Object has its own identifier mask
• Programmable FIFO mode (concatenation of Message Objects)
• Maskable interrupt
• Disabled Automatic Retransmission mode for Time Triggered CAN applications
• Programmable loop-back mode for self-test operation
• 8-bit non-multiplex Motorola HC08 compatible module interface
• two 16-bit module interfaces to the AMBA APB bus from ARM