449
Chapter 14
FCAN Interface Function
Preliminary User’s Manual U15839EE1V0UM00
14.2.8 Remote frame handling
The FCAN macro offers enhanced features for generating remote frames and for the reaction of a CAN
module upon remote frames.
(1)
Generation of a remote frame
According to the CAN specification a remote frame has the same format as a data frame except
the RTR bit of the control field, which has recessive level, and the data field, which is omitted com-
pletely.
By means of a remote frame, receiving nodes can request the transmitting node of a particular
message for sending an update of that message to the CAN bus. Usually remote frames are gen-
erated from CAN nodes which do not provide the requested message by themselves.
In the FCAN system a remote frame is automatically sent, when setting the transmit request bit
(TRQ) of the M_STATm register for a message buffer defined as receive message buffer (m = 00
to 31). Same as for generating a data frame from a transmit message buffer, the ready bit (RDY) of
M_STATm register must be set (1).
Remote frames can also be generated by means of a transmit message buffer by setting the RTR
bit of the M_CTRLm register, and using the same transmission procedure as for data frames.
However, from application point of view that method is not recommended, because it consumes
message buffer resources unnecessarily. A data frame in a CAN network can be provided, i.e.
transmitted, by only one node. All other nodes in the network may receive that data frame. Using a
transmit message buffer for a remote frame generation means that two message buffers for han-
dling of one message within one node are required - one receive message buffer for the reception
of a data frame, and the transmit message buffer explicitly for the remote frame generation.
Summary of Contents for mPD703128
Page 6: ...6 Preliminary User s Manual U15839EE1V0UM00 ...
Page 20: ...20 Preliminary User s Manual U15839EE1V0UM00 ...
Page 32: ...32 Preliminary User s Manual U15839EE1V0UM00 MEMO ...
Page 154: ...154 Preliminary User s Manual U15839EE1V0UM00 MEMO ...
Page 238: ...238 Preliminary User s Manual U15839EE1V0UM00 MEMO ...
Page 356: ...356 Preliminary User s Manual U15839EE1V0UM00 MEMO ...
Page 522: ...522 Preliminary User s Manual U15839EE1V0UM00 MEMO ...
Page 600: ...600 Preliminary User s Manual U15839EE1V0UM00 MEMO ...
Page 610: ...610 Preliminary User s Manual U15839EE1V0UM00 ...
Page 612: ......