Functional Description
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SWRU543–January 2019
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Cortex
®
-M4 Processor
Table 2-2. Processor Register Map (continued)
Offset Name Type Reset Description
– LR R/W 0xFFFF.FFFF Link register
– PC R/W – Program counter
– PSR R/W 0x0100.0000 Program Status register
– PRIMASK R/W 0x0000.0000 Priority Mask register
– FAULTMASK R/W 0x0000.0000 Fault Mask register
– BASEPRI R/W 0x0000.0000 Base Priority Mask register
– CONTROL R/W 0x0000.0000 Control register
– FPSC R/W – Floating-Point Status Control (N/A for CC32xx)
2.2.2.2 Register Descriptions
This section lists and describes the Cortex
®
-M4 registers. The core registers are not memory-mapped, and
are accessed by register name rather than offset.
NOTE: The register type shown in the register descriptions refers to type during program execution
in thread mode and handler mode. Debug access may differ.
The R0–R12 registers are 32-bit general-purpose registers for data operations, and can be accessed from
either privileged or unprivileged mode.
2.2.2.2.1 Stack Pointer (SP)
In thread mode, the function of this register changes depending on the ASP bit in the Control (CONTROL)
register. When the ASP bit is clear, this register is the main stack pointer (MSP). When the ASP bit is set,
this register is the process stack pointer (PSP). On reset, the ASP bit is clear, and the processor loads the
MSP with the value from address 0x0000 0000. The MSP can be accessed only in privileged mode; the
PSP can be accessed in either privileged or unprivileged mode.
2.2.2.2.2 Link Register (LR)
The Link register (LR) stores the return information for subroutines, function calls, and exceptions. The
Link register can be accessed from either privileged or unprivileged mode.
EXC_RETURN is loaded into the LR on exception entry.
2.2.2.2.3 Program Counter (PC)
The program counter (PC) register contains the current program address. On reset, the processor loads
the PC with the value of the reset vector, which is at address 0x0000 0004. Bit 0 of the reset vector is
loaded into the THUMB bit of the EPSR at reset and must be 1. The PC register can be accessed in either
privileged or unprivileged mode.
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