ATSAM3U-EK Atmel, ATSAM3U-EK Datasheet - Page 67

• Manufacturer Part Number: ATSAM3U-EK
• Description: KIT EVAL FOR AT91SAM3U CORTEX
• Manufacturer: Atmel
• Type: MCUr

Specifications of ATSAM3U-EK

• Contents: Board
• Processor To Be Evaluated: SAM3U
• Data Bus Width: 32 bit
• Interface Type: RS-232, USB
• Operating Supply Voltage: 3 V
• Silicon Manufacturer: Atmel
• Core Architecture: ARM
• Core Sub-architecture: Cortex - M3
• Silicon Core Number: SAM3U4E
• Silicon Family Name: SAM3U
• Kit Contents: Board CD Docs
• Rohs Compliant: Yes
• For Use With/related Products: AT91SAM3U
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

13.3.3.15
• Active stack pointer
Defines the current stack:
0 = MSP is the current stack pointer
1 = PSP is the current stack pointer.
In Handler mode this bit reads as zero and ignores writes.
• Thread mode privilege level
Defines the Thread mode privilege level:
0 = privileged
1 = unprivileged.
Handler mode always uses the MSP, so the processor ignores explicit writes to the active stack pointer bit of the CON-
TROL register when in Handler mode. The exception entry and return mechanisms update the CONTROL register.
In an OS environment, ARM recommends that threads running in Thread mode use the process stack and the kernel and
exception handlers use the main stack.
By default, Thread mode uses the MSP. To switch the stack pointer used in Thread mode to the PSP, use the MSR instruc-
tion to set the Active stack pointer bit to 1, see
When changing the stack pointer, software must use an ISB instruction immediately after the MSR instruction. This
ensures that instructions after the ISB execute using the new stack pointer. See
6430D–ATARM–25-Mar-11
31
23
15
7
CONTROL register
30
22
14
6
The CONTROL register controls the stack used and the privilege level for software execution
when the processor is in Thread mode. See the register summary in
its attributes. The bit assignments are:
29
21
13
5
Reserved
“MSR” on page
28
20
12
4
Reserved
Reserved
Reserved
160.
27
19
11
3
“ISB” on page 158
26
18
10
2
Active Stack
SAM3U Series
Table 13-2 on page 59
Pointer
25
17
9
1
Thread Mode
Privilege
Level
24
16
8
0
for
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