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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—Intel XScale
®
Processor
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
106
Order Number: 306262-004US
3.5.1.11
Register 10: TLB Lock Down
Register 10 is used for locking down entries into the instruction TLB, and data TLB.
(The protocol for locking down entries can be found in
.) Lock/unlock operations on a TLB when the MMU is disabled have
an undefined effect.
This register should be accessed as write-only. Reads from this register, as with an
MRC, have an undefined effect.
shows the command for locking down entries in the instruction TLB, and data
TLB. The entry to lock is specified by the virtual address in Rd.
3.5.1.12
Register 11-12: Reserved
These registers are reserved. Reading and writing them yields unpredictable results.
3.5.1.13
Register 13: Process ID
The Intel XScale processor supports the remapping of virtual addresses through a
Process ID (PID) register. This remapping occurs before the instruction cache,
instruction TLB, data cache and data TLB are accessed. The PID register controls when
virtual addresses are remapped and to what value.
The PID register is a 7-bit value that is ORed with bits 31:25 of the virtual address
when they are zero. This action effectively remaps the address to one of 128 “slots” in
the 4 Gbytes of address space. If bits 31:25 are not zero, no remapping occurs. This
feature is useful for operating system management of processes that may map to the
same virtual address space. In those cases, the virtually mapped caches on the Intel
XScale processor would not require invalidating on a process switch.
Table 24.
TLB Lockdown Functions
Function
opcode_2
CRm
Data
Instruction
Translate and Lock I TLB entry
0b000
0b0100
MVA
MCR p15, 0, Rd, c10, c4, 0
Translate and Lock D TLB entry
0b000
0b1000
MVA
MCR p15, 0, Rd, c10, c8, 0
Unlock I TLB
0b001
0b0100
Ignored
MCR p15, 0, Rd, c10, c4, 1
Unlock D TLB
0b001
0b1000
Ignored
MCR p15, 0, Rd, c10, c8, 1
Table 25.
Accessing Process ID
Function
opcode_2
CRm
Instruction
Read Process ID Register
0b000
0b0000
MRC p15, 0, Rd, c13, c0, 0
Write Process ID Register
0b000
0b0000
MCR p15, 0, Rd, c13, c0, 0
Table 26.
Process ID Register
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
Process ID
reset value: 0x0000,0000
Bits
Access
Description
31:25
Read / Write
Process ID - This field is used for remapping the virtual
address when bits 31-25 of the virtual address are zero.
24:0
Read-as-Zero / Write-as-Zero
Reserved - Should be programmed to zero for future
compatibility