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Section 20 Controller Area Network
R01UH0134EJ0400 Rev. 4.00 Page 995 of 2108
Sep 24, 2014
SH7262 Group, SH7264 Group
ATX (Automatic Transmission of Data Frame): When this bit is set to ‘1’ and a Remote Frame
is received into the Mailbox DLC is stored. Then, a Data Frame is transmitted from the same
Mailbox using the current contents of the message data and updated DLC by setting the
corresponding TXPR automatically. The scheduling of transmission is still governed by ID
priority or Mailbox priority as configured with the Message Transmission Priority control bit
(MCR.2). In order to use this function, MBC[2:0] needs to be programmed to be ‘001’ (Bin).
When a transmission is performed by this function, the DLC (Data Length Code) to be used is the
one that has been received. Application needs to guarantee that the DLC of the remote frame
correspond to the DLC of the data frame requested.
Important: When ATX is used and MBC = 001 (Bin) the filter for the IDE bit cannot be used
since ID of remote frame has to be exactly the same as that of data frame as the reply message.
Important: Please note that, when this function is used, the RTR bit will never be set despite
receiving a Remote Frame. When a Remote Frame is received, the CPU will be notified by the
corresponding RFPR set, however, as this module needs to transmit the current message as a Data
Frame, the RTR bit remains unchanged.
Important: Please note that in case of overrun condition (UMSR flag set when the Mailbox has
its NMC = 0) the message received is discarded. In case a remote frame is causing overrun into a
Mailbox configured with ATX = 1, the transmission of the corresponding data frame may be
triggered only if the related PFPR flag is cleared by the CPU when the UMSR flag is set. In such
case PFPR flag would get set again.
ATX Description
0 Automatic Transmission of Data Frame disabled (Initial value)
1 Automatic Transmission of Data Frame enabled
DART (Disable Automatic Re-Transmission): When this bit is set, it disables the automatic re-
transmission of a message in the event of an error on the CAN bus or an arbitration lost on the
CAN bus. In effect, when this function is used, the corresponding TXCR bit is automatically set at
the start of transmission. When this bit is set to '0', this module tries to transmit the message as
many times as required until it is successfully transmitted or it is cancelled by the TXCR.
DART Description
0 Re-transmission enabled (Initial value)
1 Re-Transmission disabled