CHAPTER 11 FCAN CONTROLLER
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User’s Manual U14492EJ3V0UD
(ii) DBT (data bit time) setting
DBT is calculated as below.
•
DBT = BTL
×
(a + 1) : [7
≤
a
≤
24]
Value a is set using bits 4 to 0 (DBT4 to DBT0) of the C1SYNC register.
DBT = BTL
×
16
= BTL
×
(a + 1)
thus a = 15
Therefore, C1SYNC register’s bits DBT4 to DBT0 = 01111B
Note that 1/DBT = f
BTL
/16
≅
1333 kHz/16
≅
83 kbps (nearly equal to the CAN bus baud rate)
(iii) SPT (sampling point) setting
Given SJW = 3:
SJW < DBT – SPT
3 < 15 – SPT
SPT < 12
Therefore, SPT is set as 11 (max.).
SPT is calculated as below.
•
SPT = BTL
×
(a + 1) : [4
≤
a
≤
16]
Value a is set using bits 9 to 5 (SPT4 to SPT0) of the C1SYNC register.
SPT = BTL
×
12
= BTL
×
(11 + 1)
thus a = 11
(iv) SJW (synchronization jump width) setting
SJW is calculated as below.
•
SJW = BTL
×
(a + 1) : [0
≤
a
≤
3]
Value a is set using bits11 and 10 (SJW1, SJW0) of the C1SYNC register.
C1SYNC register’s bits SJW1 and SJW0 = BTL
×
3
= BTL
×
(2 + 1)
thus a = 2
The C1SYNC register settings based on these results are shown in Figure 11-46 below.
Содержание V850E/IA1 mPD703116
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