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# CCSIDR2, Current Cache Size ID Register 2

The CCSIDR2 characteristics are:

## Purpose

Provides information about the architecture of the currently selected cache.

## Configuration

AArch32 System register CCSIDR2 bits [31:0] are architecturally mapped to AArch64 System register CCSIDR2_EL1[31:0].

This register is present only when EL1 is capable of using AArch32 and FEAT_CCIDX is implemented. Otherwise, direct accesses to CCSIDR2 are UNDEFINED.

The implementation includes one CCSIDR2 for each cache that it can access. CSSELR and the Security state select which Cache Size ID Register is accessible.

## Attributes

CCSIDR2 is a 32-bit register.

## Field descriptions

31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0
RES0 | NumSets

#### Bits [31:24]

Reserved, RES0.

#### NumSets, bits [23:0]

(Number of sets in cache) - 1, therefore a value of 0 indicates 1 set in the cache. The number of sets does not have to be a power of 2.

## Accessing CCSIDR2

If CSSELR.{Level, InD} is programmed to a cache level that is not implemented, then on a read of the CCSIDR2 the behavior is CONSTRAINED UNPREDICTABLE, and can be one of the following:

- The CCSIDR2 read is treated as NOP.
- The CCSIDR2 read is UNDEFINED.
- The CCSIDR2 read returns an UNKNOWN value.

Accesses to this register use the following encodings in the System register encoding space:

#### MRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

coproc | opc1 | CRn | CRm | opc2
--- | --- | --- | --- | ---
0b1111 | 0b001 | 0b0000 | 0b0000 | 0b010

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T0 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T0 == '1' then AArch32.TakeHypTrapException(0x03); elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TID2 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && !ELUsingAArch32(EL2) && IsFeatureImplemented(FEAT_EVT) && HCR_EL2.TID4 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.TID2 == '1' then AArch32.TakeHypTrapException(0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && IsFeatureImplemented(FEAT_EVT) && HCR2.TID4 == '1' then AArch32.TakeHypTrapException(0x03); else R[t] = CCSIDR2; elsif PSTATE.EL == EL2 then R[t] = CCSIDR2; elsif PSTATE.EL == EL3 then R[t] = CCSIDR2;

AArch32 Registers | AArch64 Registers | AArch32 Instructions | AArch64 Instructions | Index by Encoding | External Registers | External Registers by Offset | Registers by Functional Group | Proprietary Notice

26/03/2024 09:49; 67c0ae5282a7629ba0ea0ba7267b43cd4f7939f6

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