CHAPTER 11 FCAN CONTROLLER
544
User’s Manual U14492EJ3V0UD
11.8.7 Baud rate control function
(1) Prescaler
The V850E/IA1 includes a prescaler for dividing the CAN module clock (f
MEM
). This prescaler generates a
clock (f
BTL
) that is based on a division ratio ranging from 2 to 128 applied to the CAN module clock when the
C1BRP register’s TLM bit = 0 and based on a division ratio ranging from 2 to 256 applied to the CAN module
clock when the TLM bit = 1 (refer to
11.10 (26) CAN1 bit rate prescaler register (C1BRP)
).
(2) Nominal bit time (8 to 25 time quantum)
A definition of 1 data bit time is shown below.
Remark
1 time quantum = 1/f
BTL
Figure 11-20. Nominal Bit Time
Nominal bit time
SJW
SJW
Phase segment 2
Phase segment 1
Sample point
Prop segment
Sync segment
Segment Name
Segment Length
Description
Sync segment
(Synchronization Segment)
1
This segment begins when resynchronization occurs.
Prop segment
(Propagation Segment)
1 to 8 (programmable)
This segment is used to absorb the delays caused by
the output buffer, CAN bus, and input buffer.
It is set to return an ACK signal until phase segment 1
begins.
Prop segment time
≥
(output buffer delay) + (CAN bus
delay) + (input buffer delay)
Phase segment 1
(Phase Buffer Segment 1)
1 to 8 (programmable)
Phase segment 2
(Phase Buffer Segment 2)
Maximum value from
phase segment 1, IPT
Note
(IPT = 0 to 2)
This segment is used to compensate for errors in the
data bit time. It accommodates a wide margin or error
but slows down communication speed.
SJW
(reSynchronization Jump Width)
1 to 4 (programmable)
This sets the range for bit synchronization.
Note
IPT: Information Processing Time
Содержание V850E/IA1 mPD703116
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