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Chapter 19
CAN Controller (CAN)
Preliminary User’s Manual U17566EE1V2UM00
19.3.7
Baud rate control function
(1)
Prescaler
The CAN Controller has a prescaler that divides the clock (f
CAN
) supplied to
CAN. This prescaler generates a CAN protocol layer base clock (f
TQ
) that is the
CAN module system clock (f
CANMOD
) divided by 1 to 256 (
“CnBRP - CANn
module bit rate prescaler register“ on page 693
).
(2)
Data bit time (8 to 25 time quanta)
One data bit time is defined as follows.
1 time quantum = 1/f
TQ
The CAN Controller sets time segment 1, time segment 2, and
reSynchronization Jump Width (SJW) as the data bit time, as shown in
Figure 19-18
. Time segment 1 is equivalent to the total of the propagation (prop)
segment and phase segment 1 that are defined by the CAN protocol
specification. Time segment 2 is equivalent to phase segment 2.
Figure 19-18
Segment setting
Table 19-15
Segment setting
Note
1.
IPT: Information Processing Time
2.
Reference: The CAN protocol specification defines the segments
constituting the data bit time as shown in
Figure 19-19
.
Segment name
Settable range
Notes on setting to conform to CAN
specification
Time segment 1 (TSEG1)
2TQ to 15TQ
-
Time segment 2 (TSEG2)
1TQ to 8TQ
IPT
Note
of the CAN Controller is 0TQ. To conform
to the CAN protocol specification, therefore, a
length equal to phase segment 1 must be set here.
This means that the length of time segment 1
minus 1TQ is the settable upper limit of time
segment 2.
reSynchronization Jump
Width (SJW)
1TQ to 4TQ
The settable upper limit of SJW is the length of
time segment 1 minus 1TQ.
D
a
t
a
b
it time(DBT)
Ph
as
e
s
egment 1
Prop
s
egment
S
ync
s
egment
Ph
as
e
s
egment 2
Time
s
egment 1(T
S
EG1)
Time
s
egment 2
(T
S
EG2)
Sa
mple point (
S
PT)
S
JW
electronic components distributor