Atmel Evaluation Kit AT91SAM9M10-G45-EK AT91SAM9M10-G45-EK Datenbogen

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SAM9M10 [DATASHEET]

6355F–ATARM–12-Mar-13

CP15 registers can only be accessed in privileged mode by:

• MCR (Move to Coprocessor from ARM Register) instruction is used to write an ARM register to CP15.

• MRC (Move to ARM Register from Coprocessor) instruction is used to read the value of CP15 to an ARM 

register.

Other instructions like CDP, LDC, STC can cause an undefined instruction exception.

The assembler code for these instructions is:

MCR/MRC{cond} p15, opcode_1, Rd, CRn, CRm, opcode_2.

The MCR, MRC instructions bit pattern is shown below:

Determines specific coprocessor action. Its value is dependent on the CP15 register used. For details, refer to CP15 spe-
cific register behavior.

Determines specific coprocessor operation code. By default, set to 0.

Defines the ARM register whose value is transferred to the coprocessor. If R15 is chosen, the result is unpredictable.

Determines the destination coprocessor register.

0 = MCR instruction

1 = MRC instruction

Defines the coprocessor specific code. Value is c15 for CP15.

For more details, see Chapter 2 in ARM926EJ-S TRM.

31

30

29

28

27

26

25

24

cond

1

1

1

0

23

22

21

20

19

18

17

16

opcode_1

L

CRn

15

14

13

12

11

10

9

8

Rd

1

1

1

1

7

6

5

4

3

2

1

0

opcode_2

1

CRm