at91sam9g20-cu ATMEL Corporation, at91sam9g20-cu Datasheet - Page 48

• Manufacturer Part Number: at91sam9g20-cu
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

11.4.1
• CRm[3:0]: Specified Coprocessor Action
Determines specific coprocessor action. Its value is dependent on the CP15 register used. For details, refer to CP15 spe-
cific register behavior.
• opcode_2[7:5]
Determines specific coprocessor operation code. By default, set to 0.
• Rd[15:12]: ARM Register
Defines the ARM register whose value is transferred to the coprocessor. If R15 is chosen, the result is unpredictable.
• CRn[19:16]: Coprocessor Register
Determines the destination coprocessor register.
• L: Instruction Bit
0 = MCR instruction
1 = MRC instruction
• opcode_1[23:20]: Coprocessor Code
Defines the coprocessor specific code. Value is c15 for CP15.
• cond [31:28]: Condition
For more details, see Chapter 2 in ARM926EJ-S TRM.
48
31
23
15
7
AT91SAM9G20 Preliminary
CP15 Registers Access
opcode_1
opcode_2
30
22
14
6
CP15 registers can only be accessed in privileged mode by:
Other instructions like CDP, LDC, STC can cause an undefined instruction exception.
The assembler code for these instructions is:
The MCR, MRC instructions bit pattern is shown below:
• MCR (Move to Coprocessor from ARM Register) instruction is used to write an ARM register
• MRC (Move to ARM Register from Coprocessor) instruction is used to read the value of
cond
Rd
to CP15.
CP15 to an ARM register.
MCR/MRC{cond} p15, opcode_1, Rd, CRn, CRm, opcode_2.
29
21
13
5
28
20
12
L
4
1
27
19
11
1
1
3
26
18
10
1
1
2
CRm
CRn
25
17
1
1
9
1
6384B–ATARM–15-Dec-08
24
16
0
8
1
0