Cortex™-A8 Technical Reference Manual 3.2.2. c0, Main ID Register

3.2.2. c0, Main ID Register

The purpose of the Main ID Register is to return the device ID code that contains information about the processor.

The Main ID Register is:

a read-only register common to the Secure and Nonsecure states
accessible in privileged modes only.

Figure 3.1 shows the bit arrangement of the Main ID Register.

Figure 3.1. Main ID Register format

The contents of the Main ID Register depend on the specific implementation. Table 3.4 shows how the bit values correspond with the Main ID Register functions.

Table 3.4. Main ID Register bit functions

Bits	Field	Function
[31:24]	Implementor	Indicates the implementor, ARM: `0x41`.
[23:20]	Variant	Indicates the variant number of the processor: `0x2`.
[19:16]	Architecture	Indicates that the architecture is given in the feature registers: `0xF`.
[15:4]	Primary part number	Indicates the part number, Cortex-A8: `0xC08`.
[3:0]	Revision	Indicates the revision number of the processor: `0x2`.

Note

If an Opcode_2 value corresponding to an non-implemented or reserved ID register with CRm equal to c0 and Opcode_1 = 0 is encountered, the system control coprocessor returns the value of the Main ID Register.

Table 3.5 shows the results of attempted access for each mode.

Table 3.5. Results of access to the Main ID Register^[1]

Secure privileged		Nonsecure privileged		Secure User		Nonsecure User
Read	Write	Read	Write	Read	Write	Read	Write
Data	Undefined	Data	Undefined	Undefined	Undefined	Undefined	Undefined

To access the Main ID Register, read CP15 with:

MRC p15, 0, <Rd>, c0, c0, 0 ; Read Main ID Register

See c0, Processor Feature Register 0 - c0, Instruction Set Attributes Registers 5-7 for more information on the processor features.

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