The Propagation Time Segment; Programmable Ranges Required By Can Protocol - Texas Instruments Concerto F28M35 Series Technical Reference Manual

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Parameter
Sync_Seg
Prop_Seg
Phase_Seg1
Phase_Seg2
Synchronization Jump Width (SJW)
NOTE: For proper functionality of the CAN network, the physical delay times and the oscillator's
tolerance range have to be considered.
23.12.1.1 Synchronization Segment
The Synchronization Segment (Sync_Seg) is the part of the bit time where edges of the CAN bus level are
expected to occur. If an edge occurs outside of Sync_Seg, its distance to the Sync_Seg is called the
phase error of this edge.
23.12.1.2 Propagation Time Segment
This part of the bit time is used to compensate physical delay times within the CAN network. These delay
times consist of the signal propagation time on the bus and the internal delay time of the CAN nodes.
Any CAN node synchronized to the bit stream on the CAN bus can be out of phase with the transmitter of
the bit stream, caused by the signal propagation time between the two nodes. The CAN protocol's
nondestructive bitwise arbitration and the dominant acknowledge bit provided by receivers of CAN
messages require that a CAN node transmitting a bit stream must also be able to receive dominant bits
transmitted by other CAN nodes that are synchronized to that bit stream. The example in
shows the phase shift and propagation times between two CAN nodes.
Node B
Node A
Delay A_to_B >= node output delay(A) + bus line delay(A B) + node input delay(B)
Prop_Seg >= Delay A_to_B + Delay B_to_A
Prop_Seg >= 2 • [max(node output delay+ bus line delay + node input delay)]
SPRUH22I – April 2012 – Revised November 2019
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Table 23-1. Programmable Ranges Required by CAN Protocol
Range
1 t
(fixed)
q
[1 ... 8] t
q
[1 ... 8] t
q
[1 ... 8] t
q
[1 ... 4] t
q
Figure 23-12. The Propagation Time Segment
Sync_Seg
Prop_seg
Delay A_to_B
B_to_A
Copyright © 2012–2019, Texas Instruments Incorporated
Remark
Synchronization of bus input to CAN_CLK
Compensates for the physical delay times
May be lengthened temporarily by synchronization
May be shortened temporarily by synchronization
May not be longer than either Phase Buffer Segment
Phase_seg2
Phase_seg1
Delay
®
M3 Controller Area Network (CAN)
CAN Bit Timing
Figure 23-12
1531

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