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CAN_BTIME0
(87C196CA)
Program the CAN bit timing 0 (CAN_BTIME0) register to define the length of one time quantum and
the maximum number of time quanta by which a bit time can be modified for resynchronization.
7
87C196CA
SJW1
Bit
Bit
Number
Mnemonic
7:6
SJW1:0
5:0
BRP5:0
NOTE:
The CCE bit (CAN_CON.6) must be set to enable write access to this register.
SJW0
BRP5
BRP4
Synchronization Jump Width
This field defines the maximum number of time quanta by which a resyn-
chronization can modify t
3. The hardware adds 1 to the programmed value, so a "1" value causes
the CAN peripheral to add or subtract 2 time quanta, for example. This
adjustment has no effect on the total bit time; if t
t
is decreased by 2 tq, and vice versa.
2
TSEG
Baud-rate Prescaler
This field defines the length of one time quantum (tq), using the following
formula, where t
is the input clock period on XTAL1. Valid programmed
1
XTAL
values are 0–63.
×
(
tq
2t
BRP
1
=
+
XTAL1
For example, at 20 MHz operation, the system clock period is 50 ns.
Writing 3 to BRP achieves a time quanta of 400 ns; writing 1 to BRP
achieves a time quanta of 200 ns.
(
×
)
×
(
)
tq
2
50
3
1
=
+
(
×
)
×
(
)
tq
=
2
50
1
+
1
Reset State:
BRP3
BRP2
Function
and t
. Valid programmed values are 0–
1
2
TSEG
TSEG
TSEG
)
400 ns
=
=
200 ns
REGISTERS
CAN_BTIME0
Address:
1E3FH
Unchanged
0
BRP1
BRP0
is increased by 2 tq,
1
C-11
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