913
11054A–ATARM–27-Jul-11
SAM9X25
913
11054A–ATARM–27-Jul-11
SAM9X25
• SAMPLE POINT:
The SAMPLE POINT is the point in time at which the bus level is read and interpreted as the
value of that respective bit. Its location is at the end of PHASE_SEG1.
• SJW: ReSynchronization Jump Width.
The ReSynchronization Jump Width defines the limit to the amount of lengthening or shortening
of the Phase Segments.
SJW is programmable to be the minimum of PHASE SEG1 and 4 TQ.
If the SMP field in the CAN_BR register is set, then the incoming bit stream is sampled three
times with a period of half a CAN clock period, centered on sample point.
In the CAN controller, the length of a bit on the CAN bus is determined by the parameters (BRP,
PROPAG, PHASE1 and PHASE2).
The time quantum is calculated as follows:
Note:
The BRP field must be within the range [1, 0x7F], i.e., BRP = 0 is not authorized.
To compensate for phase shifts between clock oscillators of different controllers on the bus, the
CAN controller must resynchronize on any relevant signal edge of the current transmission. The
resynchronization shortens or lengthens the bit time so that the position of the sample point is
shifted with regard to the detected edge. The resynchronization jump width (SJW) defines the
maximum of time by which a bit period may be shortened or lengthened by resynchronization.
Figure 41-5.
CAN Bit Timing
t
BIT
t
CSC
t
PRS
t
PHS1
t
PHS2
+
+
+
=
t
CSC
BRP
1
+
(
)
MCK
⁄
=
t
PRS
t
CSC
PROPAG
1
+
(
)
×
=
t
PHS1
t
CSC
PHASE1
1
+
(
)
×
=
t
PHS2
t
CSC
PHASE2
1
+
(
)
×
=
t
SJW
t
CSC
SJW
1
+
(
)
×
=
SYNC_
SEG
PROP_SEG
PHASE_SEG1
PHASE_SEG2
NOMINAL BIT TIME
Sample Point
Transmission Point
MCK
CAN Clock
t
CSC
t
PRS
t
PHS1
t
PHS2
Содержание SAM9X25
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Страница 1067: ...1067 11054A ATARM 27 Jul 11 SAM9X25 1067 11054A ATARM 27 Jul 11 SAM9X25 PTZ Pause Time Zero Enable pause time zero interrupt...
Страница 1069: ...1069 11054A ATARM 27 Jul 11 SAM9X25 1069 11054A ATARM 27 Jul 11 SAM9X25 PTZ Pause Time Zero Disable pause time zero interrupt...
Страница 1071: ...1071 11054A ATARM 27 Jul 11 SAM9X25 1071 11054A ATARM 27 Jul 11 SAM9X25 PTZ Pause Time Zero Pause time zero interrupt masked...
Страница 1128: ...1128 11054A ATARM 27 Jul 11 SAM9X25 1128 11054A ATARM 27 Jul 11 SAM9X25...
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Страница 1131: ...1131 11054A ATARM 27 Jul 11 SAM9X25 Revision History Doc Rev 11054A Comments Change Request Ref 1st issue...
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