Atmel ARM-Based Evaluation Kit AT91SAM9N12-EK AT91SAM9N12-EK Data Sheet

ARM DDI0198D

B-11

Table B-8 describes the entry-select bit fields in the Rd register.

2.

Use the following MMU Test Register instructions to access the MVA tag:

MRC p15, 4, <Rd>, c15, c2, 1 ; read lockdown TLB

MCR p15, 4, <Rd>, c15, c3, 1 ; write lockdown TLB

See Figure B-3 on page B-7 for read or write data in the Rd register.

3.

Use the following MMU Test Register instructions to read or write the PA and 
access permission data:

MRC p15, 4, <Rd>, c15, c4, 1 ; read PA and access permission data

MCR p15, 4, <Rd>, c15, c5, 1 ; write PA and access permission data

See Figure B-4 on page B-8 for the read or write data in the Rd register.

4.

Use the following instruction to complete a write to an entry:

MCR p15, 4, <Rd>, c15, c7, 1 ; transfer lockdown storage into RAM

To write an entry into the lockdown TLB, the full sequence is therefore:

MCR p15, 4/5, <Rd>, c15, c3, 1 ; write tag lockdown TLB storage reg
MCR p15, 4/5, <Rd>, c15, c5, 1 ; write PA/PROT lockdown TLB storage reg
MCR p15, 4/5, <Rd>, c15, c7, 1 ; transfer lockdown storage into RAM

To read an entry from the lockdown TLB, the entry must first be written using the above 
instructions. The entry can then be read using the following instructions:

MRC p15, 4/5, <Rd>, c15, c2, 1 ; read tag lockdown TLB
MRC p15, 4/5, <Rd>, c15, c4, 1 ; read PA/PROT lockdown TLB

SBZ

28

26

SBZ

Indexed

entry

31

29

0

25

[31:29]

-

Should Be Zero

[28:26]

Indexed entry

Indexed entry in lockdown TLB

[25:0]

-

Should Be Zero