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Registers, 1 can clock control register, Registers 3.1 can clock control register – FUJITSU MB91460 SERIES FR60 User Manual

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Chapter 15 CAN Clock Prescaler

3.Registers

3. Registers

3.1 CAN Clock Control Register

Controls the CAN clock source, the clock division ratio and the clock disable.

• CANPRE: Address 04C0h (Access: Byte)

(See “

Meaning of Bit Attribute Symbols (Page No.10)

” for details of the attributes.)

• Bit7-6: Reserved bitAlways write “0” to these register bits.

• Bit5-4: CAN Prescaler ClocK Selection

• Bit3-0: Source clock Divide-by-C selection

(Note)

Do not exceed the specified upper frequency limit of CANCLK (e.g. 20 MHz) e.g. by setting prescaler
values exceeding this limit, or by switching the prescaler clock source to a higher frequency clock
without switching previously the prescaler values to higher division rates.

(Note)

If prescaler source is selected to PLL output: Even though it is possible to select no division ratio (:1)
for the divide-by-C counter it is not recommended. The resulting output clock will have an odd clock
duty ratio (direct PLL output can have up to 90:10 duty). Always select at least a division ratio > 1.

• CANCKD: Address 04C1h (Access: Byte)

7

6

5

4

3

2

1

0

bit

-

-

CPCKS1

CPCKS0

DVC3

DVC2

DVC1

DVC0

0

0

0

0

0

0

0

0

Initial value (

INIT pin input,

watchdog reset

)

0

0

X

X

X

X

X

X

Initial value

(Software reset)

R0/W0

R0/W0

R/W

R/W

R/W

R/W

R/W

R/W

Attribute

CPCKS1-CPCKS0

Prescaler clock source

00

CLKB, core clock (inital)

01

PLL output

10

reserved

11

Main oscillation

DVC3-DVC0

Source clock divided-by-C (generates CANCLK)

0000

Source clock : 1 (no division)

0001

Source clock

: 2 (division by 2)

0010

Source clock

: 3 (division by 3)

0011

Source clock

: 4 (division by 4)

0100

Source clock

: 5 (division by 5)

0101

Source clock

: 6 (division by 6)

0110

Source clock

: 7 (division by 7)

0111

Source clock

: 8 (division by 8)

......

.....

1111

Source clock

: 16 (division by 16)

7

6

5

4

3

2

1

0

bit

-

-

CANCKD5 CANCKD4 CANCKD3 CANCKD2 CANCKD1 CANCKD0

0

0

0

0

0

0

0

0

Initial value (

INIT pin input,

watchdog reset

)