LM4F232H5QCFIG Datasheet, PDF (74/1472 Pages) Texas Instruments – Stellaris® LM4F232H5QC Microcontroller

The Cortex-M4F Processor
2.3.2
2.3.3
Only privileged software can write to the CONTROL register to change the privilege level for software
execution in Thread mode. Unprivileged software can use the SVC instruction to make a supervisor
call to transfer control to privileged software.
Stacks
The processor uses a full descending stack, meaning that the stack pointer indicates the last stacked
item on the memory. When the processor pushes a new item onto the stack, it decrements the stack
pointer and then writes the item to the new memory location. The processor implements two stacks:
the main stack and the process stack, with a pointer for each held in independent registers (see the
SP register on page 78).
In Thread mode, the CONTROL register (see page 88) controls whether the processor uses the
main stack or the process stack. In Handler mode, the processor always uses the main stack. The
options for processor operations are shown in Table 2-1 on page 74.
Table 2-1. Summary of Processor Mode, Privilege Level, and Stack Use
Processor Mode
Use
Thread
Applications
Handler
Exception handlers
a. See CONTROL (page 88).
Privilege Level
Privileged or unprivileged ^a
Always privileged
Stack Used
Main stack or process stack ^a
Main stack
Register Map
Figure 2-3 on page 75 shows the Cortex-M4F register set. Table 2-2 on page 75 lists the Core
registers. The core registers are not memory mapped and are accessed by register name, so the
base address is n/a (not applicable) and there is no offset.
74
November 08, 2011
Texas Instruments-Advance Information