MC68HC05X16 Datasheet, PDF (63/232 Pages) Freescale Semiconductor, Inc – High-density complementary metal oxide semiconductor HCMOS) microcontroller unit

Freescale Semiconductor, Inc.
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MOTOROLA CAN MODULE (MCAN)
The MCAN includes all hardware modules necessary to implement the CAN transfer layer, which
represents the kernel of the CAN bus protocol as defined by BOSCH GmbH, the originators of the
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CAN specification. For full details of the CAN protocol please refer to the published specifications.
Up to the message level, the MCAN is totally compatible with the full CAN implementation.
Functional differences are related to the object layer only. Whereas a full CAN controller provides
dedicated hardware for handling a set of messages, the MCAN is restricted to receiving and/or
transmitting messages on a message by message basis.
The MCAN will never initiate an overload frame. If the MCAN starts to receive a valid message
(one that passes the acceptance filter) and there is no receive buffer available for it then the
overrun flag in the CPU status register will be set. The MCAN will respond to overload frames
generated by other CAN nodes, as required by the CAN protocol. A summary of all the MCAN
frame formats is given in Figure 5-2 for reference. A diagram of the major blocks of the MCAN is
shown in Figure 5-1.
Interface
management
logic
Transmit
buffer
Receive
buffer 0
Receive
buffer 1
Microprocessor related logic
Bit timing
logic
Transceive
logic
Line
interface
logic
Error
management
logic
Bit stream
processor
Bus line related logic
Figure 5-1 MCAN block diagram
MCAN
bus
line
MC68HC05X16
MOTOROLA CAN MODULE (MCAN)
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