Maxim Integrated High-Speed Microcontroller Users Guide: Network Microcontroller Supplement - Manual (Page 150)

High-Speed Microcontroller User’s
Guide: Network Microcontroller
Supplement
150
Figure 19-5. Acknowledge Field
End of frame: (Standard and extended format) The end of frame for both the data and remote frame is established by the transmitter
sending 7 recessive bits.
Interframe spacing (intermission): (Standard and extended format) Data frames and remote frames are separated from preceding
frames by three recessive bits termed the intermission. During the intermission, the only allowed signaling to the bus is by an overload
condition. No node is allowed to start a message transmission of a data or remote frame during this period. If no node becomes active
following the interframe space, an indeterminate number of recessive bit times transpire in the bus idle condition until the next trans-
mission of a new data or remote frame by a node.
Figure 19-6. Intermission
Remote frame: (Standard and extended format) The remote frame is transmitted by a CAN controller to request the transmission of
the data frame with the same identifier. The remote frame is composed of seven fields. These are the start of frame, arbitration field,
control field, data field, CRC field, acknowledge field, and an end of frame.
Figure 19-7. Remote Frame
The remote frame is used when a CAN processor wishes to request data from another node. Sending a remote frame initiates a trans-
mission of data from a source node with the same identifier (masked groups included). The primary bit pattern difference between a
data frame and a remote frame is the RTR bit, which is sent as a recessive bit in the remote frame and is sent as a dominant bit in the
data frame. The remote frame also does not contain a data field, being independent of the programmed values in the
DTBYC3–DTBYC0 bits in the respective CAN message format register.
S
O
F
Arbitration Field
Remote Frame
ACK Field
Interframe Space
or Overload Frame
End of
Frame
Control Field CRC Field
Interframe
Space
ACK
Slot
ACK Delimiter
End of Frame CRC Field ACK Field
Bus Idle
Frame Frame Interframe Space
Intermisson
Maxim Integrated