LM3S1968 Datasheet, PDF (101/709 Pages) List of Unclassifed Manufacturers – Microcontroller

Stellaris^® LM3S1968 Microcontroller
Table 3-3. TEX, S, C, and B Bit Field Encoding (continued)
TEX
S
C
B
Memory Type
1BB
0
A
A
Normal
1BB
1
A
A
Normal
Shareability
Not shareable
Shareable
a. The MPU ignores the value of this bit.
Other Attributes
Cached memory (BB =
outer policy, AA = inner
policy).
See Table 3-4 for the
encoding of the AA and
BB bits.
Table 3-4 on page 101 shows the cache policy for memory attribute encodings with a TEX value in
the range of 0x4-0x7.
Table 3-4. Cache Policy for Memory Attribute Encoding
Encoding, AA or BB
00
01
10
11
Corresponding Cache Policy
Non-cacheable
Write back, write and read allocate
Write through, no write allocate
Write back, no write allocate
Table 3-5 on page 101 shows the AP encodings in the MPUATTR register that define the access
permissions for privileged and unprivileged software.
Table 3-5. AP Bit Field Encoding
AP Bit Field
000
001
010
Privileged
Permissions
No access
R/W
R/W
Unprivileged
Permissions
No access
No access
RO
011
R/W
R/W
100
Unpredictable
Unpredictable
101
RO
No access
110
RO
RO
111
RO
RO
Description
All accesses generate a permission fault.
Access from privileged software only.
Writes by unprivileged software generate a
permission fault.
Full access.
Reserved.
Reads by privileged software only.
Read-only, by privileged or unprivileged software.
Read-only, by privileged or unprivileged software.
MPU Configuration for a Stellaris Microcontroller
Stellaris microcontrollers have only a single processor and no caches. As a result, the MPU should
be programmed as shown in Table 3-6 on page 101.
Table 3-6. Memory Region Attributes for Stellaris Microcontrollers
Memory Region
Flash memory
Internal SRAM
External SRAM
Peripherals
TEX
000b
000b
000b
000b
S
C
B
Memory Type and Attributes
0
1
0
Normal memory, non-shareable, write-through
1
1
0
Normal memory, shareable, write-through
1
1
1
Normal memory, shareable, write-back,
write-allocate
1
0
1
Device memory, shareable
July 15, 2014
101
Texas Instruments-Production Data