AP29000
Connecting C166 and C500 Microcontroller to CAN
The Infineon CAN Devices C167CR, C515C and SAE 81C90/91
Application Note 28 V 1.0, 2004-02
It has an additional individually programmable acceptance mask for the complete
Arbitration Field called Mask of Last Message which is ANDed with the global mask
that corresponds to the incoming message. This allows classes of messages to be
especially received in this message object by masking some (or all) bits of the
identifier.
4.2.3 The Message Objects
The CAN controller provides storage for up to 15 message objects of maximum 8
bytes data length. Each of these objects has a unique identifier and its own set of
control and status bits (see figure 3.2-4a and 3.2-4b). Each object can be configured
with its direction as either transmit or receive, except the last message which is only a
receive buffer with a special mask register.
An object with its direction set as transmit can be configured to be automatically sent
whenever a Remote Frame with a matching identifier (taking into account the
respective global mask register) is received over the CAN bus. By requesting the
transmission of a message with the direction set as receive, a Remote Frame can be
sent to request that the appropriate object be sent by some other node. Each object
has separate transmit and receive interrupts and status bits, allowing the CPU full
flexibility in detecting when a Remote/Data Frame has been sent or received.
For general purpose two masks for acceptance filtering can be programmed, one for
identifiers of 11 bits and one for identifiers of 29 bits. However the CPU must configure
bit XTD (Normal or Extended Frame Identifier) for each valid message to determine
whether a standard or extended frame will be accepted.
The last message object has its own programmable mask for acceptance filtering,
allowing a large number of infrequent objects to be handled by the system.
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