MDK-ARM Keil, MDK-ARM Datasheet - Page 144

• Manufacturer Part Number: MDK-ARM
• Description: KIT REALVIEW MCU DEVELOPMENT
• Manufacturer: Keil
• Type: Compiler and IDEr

Specifications of MDK-ARM

• For Use With/related Products: ARM MCUs
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

144
Chapter 6. RL-CAN Introduction
provides error detection and correction from the start of frame up to the
beginning of the CRC field.
After the CRC, there is an acknowledge slot. The transmitting node expects the
receiving nodes to insert an acknowledgement in this slot within the transmitting
CAN frame. In practice, the transmitter sends a recessive bit and any node,
which has received the CAN message up to this point, will assert a dominant bit
on the bus, thus generating the acknowledgement. This means, that the
transmitter will be satisfied if just one node acknowledges its message, or if 100
nodes generate the acknowledgement. This needs to be taken into account when
developing your application layer. Care must be taken to treat the acknowledge
as a weak acknowledge, rather than assuming that it is confirmation that the
message has reached all its destination nodes. After the acknowledge slot, there
is an end-of-frame message delimiter.
The Remote Transmit Request (RTR) frame is used to request message packets
from the network as a master/slave transaction. Each CAN may also transmit a
remote transmit request frame RTR. The purpose of this frame is to request a
specific message frame from the network. The structure of the RTR frame is the
same as the message frame except that it does not have a data field.
A node can use an RTR frame to
request a specific message frame
from the CAN network. To do
this, the requesting node sends
an RTR frame. The Identifier is
set to the address of the message
frame it wants to receive and the
RTR bit is set to one. When the
RTR frame is transmitted, it is broadcasted onto the network and received by all
the network nodes. Each node will see it as a remote request and will examine
the message identifier. The node that normally transmits that message identifier
will then reply with a standard message frame (RTR bit = 0), which includes the
requested message identifier and its current data.