CHAPTER 19 FCAN CONTROLLER (V850/SC3)
User’s Manual U15109EJ3V0UD
676
Given the above limit values, the following four settings are possible.
Prescaler
DBT
SPT (MAX.)
Calculated SPT
24
8
5
5/8 = 62.5%
16
12
9
9/12 = 75%
12
16
13
13/16 = 81%
8
24
17
17/24 = 71%
16 MHz/83 Kbps
≅
192 = 64
×
3
<1>
= 48
×
4
<2>
= 32
×
6
<3>
= 24
×
8
<4>
= 16
×
12
<5>
= 12
×
16
<6>
= 8
×
24
<7>
= 6
×
32
<8>
= 4
×
48
<9>
= 3
×
64
<10>
The settings that can actually be made for the V850/SC3 are in the range from <4> to <7> above (the section
enclosed in broken lines).
Among these options in the range from <4> to <7> above, option <6> is the ideal setting when actually setting
the register.
(i) Prescaler (CAN protocol layer basic system clock: f
BTL
) setting
f
BTL
is calculated as shown below.
•
f
BTL
= f
MEM
/{(a + 1)
×
2} : [0
≤
a
≤
63]
Value a is set using bits 5 to 0 (BRP5 to BRP0) of the CnBRP register.
f
BTL
= 16 MHz/12
= 16 MHz/{(5 + 1)
×
2}
thus a = 5
Therefore, CnBRP register = 0005H