SAF-C164SM Infineon Technologies, SAF-C164SM Datasheet - Page 357

• Manufacturer Part Number: SAF-C164SM
• Description: 16-Bit CMOS Microcontroller
• Manufacturer: Infineon Technologies

Bit
RMTPND
1)
2)
3)
Arbitration Registers
The Arbitration Registers (UARn&LARn) are used for acceptance filtering of incoming
messages and to define the identifier of outgoing messages. A received message with
a matching identifier is accepted as a data frame (matching object has DIR = ‘0’) or as a
remote frame (matching object has DIR = ‘1’). For matching, the corresponding Global
Mask must be considered (the Mask of Last Message must also be considered for
message object 15). Extended frames (using Global Mask Long) can be stored only in
message objects with XTD = ‘1’, standard frames (using Global Mask Short) can be
stored only in message objects with XTD = ‘0’.
Message objects should have unique identifiers such that if some bits are masked out
by the Global Mask Registers (“don’t care” bits), then the identifiers of the valid message
objects should differ in the remaining bits which are used for acceptance filtering.
If a received message (data frame or remote frame) matches with more than one valid
message object, it is associated with the object having the lowest message number.
Thus, a received data frame is stored in the “lowest” object, or the “lowest” object is sent
in response to a remote frame. The Global Mask is used for this matching.
User’s Manual
In message object 15 (last message) these bits are hardwired to “0” (inactive) in order to prevent transmission
of message 15.
When the CAN controller writes new data into the message object, unused message bytes will be overwritten
by non specified values. Usually the CPU will clear this bit before working on the data, and verify that the bit is
still cleared once it has finished working to ensure that it has worked on a consistent set of data and not part
of an old message and part of the new message.
For transmit-objects the CPU will set this bit along with clearing bit CPUUPD. This will ensure that, if the
message is actually being transmitted during the time the message was being updated by the CPU, the CAN
controller will not reset bit TXRQ. In this way bit TXRQ is only reset once the actual data has been transferred.
When the CPU requests the transmission of a receive-object, a remote frame will be sent instead of a data
frame to request a remote node to send the corresponding data frame. This bit will be cleared by the CAN
controller along with bit RMTPND when the message has been successfully transmitted, if bit NEWDAT has
not been set.
If there are several valid message objects with pending transmission request, the message with the lowest
message number is transmitted first. This arbitration is done when several objects are requested for
transmission by the CPU, or when operation is resumed after an error frame or after arbitration has been lost.
Function
Remote Pending (Used for transmit-objects)
Indicates that the transmission of this message object has been
requested by a remote node, but the data has not yet been transmitted.
When RMTPND is set, the CAN controller also sets TXRQ. Bits
RMTPND and TXRQ are cleared when the message object has been
successfully transmitted.
19-20
On-Chip CAN Interface
C164CM/C164SM
Derivatives
V1.0, 2002-02