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CHAPTER 19 FCAN CONTROLLER (V850/SC3)
User’s Manual U15109EJ3V0UD
653
19.11.7 Baud rate control function
(1) Prescaler
The FCAN controller of the V850/SC3 includes a prescaler for dividing the clock supplied to the CAN (f
MEM1
).
This prescaler generates a clock (f
BTL
) that is based on a division ratio ranging from 2 to 128 applied to the
CAN base clock (f
MEM
) when the CnBRP register’s TLM bit = 0, and from 2 to 256 when the TLM bit = 1 (see
19.5.25 CANn bit rate prescaler register (CnBRP)
).
(2) Nominal bit time (8 to 25 time quanta)
The definition of 1 data bit time (1 time quantum) is shown below.
Caution
When selecting f
MEM1
as the clock (f
MEM
) to the memory access controller using the CAN main
clock select register (CGCS) and f
MEM
/2 as the CAN protocol layer base system clock (f
BTL
)
using the CANn bit rate prescaler register (CnBRP), set f
XX
≤≤≤≤
16 MHz to make one data bit
time 8 time quanta. Similarly, set f
XX
≤≤≤≤
18 MHz to make one data bit time 9 time quanta.
If used with a larger frequency than above, the baud rate exceeds 1 Mbps, which is the
maximum value of the CAN protocol.
Remark
1 time quantum = 1/f
BTL