1 /**************************************************************************************************/
2 /** \defgroup Core_Register_gr Core Register Access
3 \brief Functions to access the Cortex-M core registers.
5 The following functions provide access to Cortex-M core registers.
11 /**************************************************************************************************/
12 /** \brief Read the CONTROL register
14 The function reads the CONTROL register value using the instruction \b MRS.
16 The CONTROL register controls the stack used and the privilege level for software execution
17 when the processor is in thread mode and, if implemented, indicates whether the FPU state is
18 active. This register uses the following bits:
20 - \b CONTROL[2] [only Cortex-M4 and Cortex-M7]
25 - =0 In handler mode - MSP is selected. No alternate stack possible for handler mode.
26 - =0 In thread mode - Default stack pointer MSP is used.
27 - =1 In thread mode - Alternate stack pointer PSP is used.
29 - \b CONTROL[0] [not Cortex-M0]
30 - =0 In thread mode and privileged state.
31 - =1 In thread mode and user state.
33 \returns CONTROL register value
36 - The processor can be in user state or privileged state when running in thread mode.
37 - Exception handlers always run in privileged state.
38 - On reset, the processor is in thread mode with privileged access rights.
41 - \ref __set_CONTROL; CONTROL_Type
44 uint32_t __get_CONTROL(void);
47 /**************************************************************************************************/
48 /** \brief Set the CONTROL Register
50 The function sets the CONTROL register value using the instruction \b MSR.
52 The CONTROL register controls the stack used and the privilege level for software execution
53 when the processor is in thread mode and, if implemented, indicates whether the FPU state is
54 active. This register uses the following bits:
56 - \b CONTROL[2] [only Cortex-M4 and Cortex-M7]
61 - Writeable only when the processor is in thread mode and privileged state (CONTROL[0]=0).
62 - =0 In handler mode - MSP is selected. No alternate stack pointer possible for handler mode.
63 - =0 In thread mode - Default stack pointer MSP is used.
64 - =1 In thread mode - Alternate stack pointer PSP is used.
66 - \b CONTROL[0] [not writeable for Cortex-M0]
67 - Writeable only when the processor is in privileged state.
68 - Can be used to switch the processor to user state (thread mode).
69 - Once in user state, trigger an interrupt and change the state to privileged in the
70 exception handler (the only way).
71 - =0 In thread mode and privileged state.
72 - =1 In thread mode and user state.
75 \param [in] control CONTROL register value to set
78 - The processor can be in user state or privileged state when running in thread mode.
79 - Exception handlers always run in privileged state.
80 - On reset, the processor is in thread mode with privileged access rights.
83 - \ref __get_CONTROL; __set_PSP; __set_MSP; CONTROL_Type
86 void __set_CONTROL(uint32_t control);
89 /**************************************************************************************************/
90 /** \brief Read the IPSR register
92 The function reads the Interrupt Program Status Register (IPSR) using the instruction \b MRS.
94 The ISPR contains the exception type number of the current Interrupt Service Routine (ISR).
95 Each exception has an associated unique IRQn number. The following bits are used:
97 - \b ISR_NUMBER (IPSR[8:0])
108 - = 12 Reserved for Debug
116 \returns ISPR register value
119 - This register is read-only.
122 - \ref __get_xPSR; IPSR_Type
126 uint32_t __get_IPSR(void);
129 /**************************************************************************************************/
130 /** \brief Read the APSR register
132 The function reads the Application Program Status Register (APSR) using the instruction \b MRS.
134 The APSR contains the current state of the condition flags from instructions executed previously.
135 The APSR is essential for controlling conditional branches. The following flags are used:
137 - \b N (APSR[31]) (Negative flag)
138 - =1 The instruction result has a negative value (when interpreted as signed integer).
139 - =0 The instruction result has a positive value or equal zero.
141 - \b Z (APSR[30]) (Zero flag)
142 - =1 The instruction result is zero. Or, after a compare instruction, when the two values
145 - \b C (APSR[29]) (Carry or borrow flag)
146 - =1 For unsigned additions, if an unsigned overflow occurred.
147 - =<i>inverse of borrow output status</i> For unsigned subtract operations.
149 - \b V (APSR[28]) (Overflow flag)
150 - =1 A signed overflow occurred (for signed additions or subtractions).
152 - \b Q (APSR[27]) (DSP overflow or saturation flag) [not Cortex-M0]
153 - This flag is a \em sticky flag. Saturating and certain multiplying instructions can set the
154 flag, but cannot clear it.
155 - =1 When saturation or an overflow occurred.
157 - \b GE (APSR[19:16]) (Greater than or Equal flags) [not Cortex-M0]
158 - Can be set by the parallel add and subtract instructions.
159 - Are used by the <kbd>SEL</kbd> instruction to perform byte-based selection from two registers.
162 \returns APSR register value
165 - Some instructions update all flags; some instructions update a subset of the flags.
166 - If a flag is not updated, the original value is preserved.
167 - Conditional instructions that are not executed have no effect on the flags.
168 - The CMSIS does not provide a function to update this register.
171 - \ref __get_xPSR; APSR_Type
175 uint32_t __get_APSR(void);
178 /**************************************************************************************************/
179 /** \brief Read the xPSR register
181 The function reads the combined Program Status Register (xPSR) using the instruction \b MRS.
183 xPSR provides information about program execution and the APSR flags. It consists of the
185 \li Application Program Status Register (APSR)
186 \li Interrupt Program Status Register (IPSR)
187 \li Execution Program Status Register (EPSR)
189 In addition to the flags described in \ref __get_APSR and \ref __get_IPSR, the register provides
191 - \b IT (xPSR[26:25]) (If-Then condition instruction)
192 - Contains up to four instructions following an IT instruction.
193 - Each instruction in the block is conditional.
194 - The conditions for the instructions are either all the same, or some can be the inverse
197 - \b T (xPSR[24]) (Thumb bit)
198 - =1 Indicates that that the processor is in Thumb state.
199 - =0 Attempting to execute instructions when the T bit is 0 results in a fault or lockup.
200 - The conditions for the instructions are either all the same, or some can be the inverse
203 \returns xPSR register value
206 - The CMSIS does not provide functions that access EPSR.
209 - \ref __get_APSR; __get_IPSR; xPSR_Type
213 uint32_t __get_xPSR(void);
216 /**************************************************************************************************/
217 /** \brief Read the PSP register
219 The function reads the Process Stack Pointer (PSP) value using the instruction \b MRS.
221 Physically two different stack pointers (SP) exist:
222 - The Main Stack Pointer (MSP) is the default stack pointer after reset. It is also used when
223 running exception handlers (handler mode).
224 - The Process Stack Pointer (PSP), which can be used only in thread mode.
226 Register R13 banks the SP. The SP selection is determined by the bit[1] of the CONTROL register:
227 - =0 MSP is the current stack pointer. This is also the default SP. The initial value is loaded
228 from the first 32-bit word of the vector table from the program memory.
229 - =1 PSP is the current stack pointer. The initial value is undefined.
231 \returns PSP register value
234 - Only one of the two SPs is visible at a time.
235 - For many applications, the system can completely rely on the MSP.
236 - The PSP is normally used in designs with an OS where the stack memory for OS Kernel must
237 be separated from the application code.
240 - \ref __set_PSP; __get_MSP; __get_CONTROL
245 uint32_t __get_PSP(void);
248 /**************************************************************************************************/
249 /** \brief Set the PSP register
251 The function sets the Process Stack Pointer (PSP) value using the instruction \b MSR.
253 Physically two different stack pointers (SP) exist:
254 - The Main Stack Pointer (MSP) is the default stack pointer after reset. It is also used when
255 running exception handlers (handler mode).
256 - The Process Stack Pointer (PSP), which can be used only in thread mode.
258 Register R13 banks the SP. The SP selection is determined by the bit[1] of the CONTROL register:
259 - =0 MSP is the current stack pointer. This is also the default SP. The initial value is loaded
260 from the first 32-bit word of the vector table from the program memory.
261 - =1 PSP is the current stack pointer. The initial value is undefined.
263 \param [in] topOfProcStack PSP value to set
266 - Only one of the two SPs is visible at a time.
267 - For many applications, the system can completely rely on the MSP.
268 - The PSP is normally used in designs with an OS where the stack memory for OS Kernel must
269 be separated from the application code.
272 - \ref __get_PSP; __set_MSP; __set_CONTROL
275 void __set_PSP(uint32_t topOfProcStack);
278 /**************************************************************************************************/
279 /** \brief Read the MSP register
281 The function reads the Main Stack Pointer (MSP) value using the instruction \b MRS.
283 Physically two different stack pointers (SP) exist:
284 - The Main Stack Pointer (MSP) is the default stack pointer after reset. It is also used when
285 running exception handlers (handler mode).
286 - The Process Stack Pointer (PSP), which can be used only in thread mode.
288 Register R13 banks the SP. The SP selection is determined by the bit[1] of the CONTROL register:
289 - =0 MSP is the current stack pointer. This is also the default SP. The initial value is loaded
290 from the first 32-bit word of the vector table from the program memory.
291 - =1 PSP is the current stack pointer. The initial value is undefined.
293 \returns MSP Register value
296 - Only one of the two SPs is visible at a time.
297 - For many applications, the system can completely rely on the MSP.
298 - The PSP is normally used in designs with an OS where the stack memory for OS Kernel must
299 be separated from the application code.
302 - \ref __set_MSP; __get_PSP; __get_CONTROL
306 uint32_t __get_MSP(void);
309 /**************************************************************************************************/
310 /** \brief Set the MSP register
312 The function sets the Main Stack Pointer (MSP) value using the instruction \b MSR.
314 Physically two different stack pointers (SP) exist:
315 - The Main Stack Pointer (MSP) is the default stack pointer after reset. It is also used when
316 running exception handlers (handler mode).
317 - The Process Stack Pointer (PSP), which can be used only in thread mode.
319 Register R13 banks the SP. The SP selection is determined by the bit[1] of the CONTROL register:
320 - =0 MSP is the current stack pointer. This is also the default SP. The initial value is loaded
321 from the first 32-bit word of the vector table from the program memory.
322 - =1 PSP is the current stack pointer. The initial value is undefined.
324 \param [in] topOfMainStack MSP value to set
327 - Only one of the two SPs is visible at a time.
328 - For many applications, the system can completely rely on the MSP.
329 - The PSP is normally used in designs with an OS where the stack memory for OS Kernel must
330 be separated from the application code.
333 - \ref __get_MSP; __set_PSP; __set_CONTROL
337 void __set_MSP(uint32_t topOfMainStack);
340 /**************************************************************************************************/
341 /** \brief Read the PRIMASK register bit
343 The function reads the Priority Mask register (PRIMASK) value using the instruction \b MRS.
345 PRIMASK is a 1-bit-wide interrupt mask register. When set,
346 it blocks all interrupts apart from the non-maskable interrupt (NMI) and the hard fault exception.
347 The PRIMASK prevents activation of all exceptions with configurable priority.
349 \returns PRIMASK register value
351 - =1 prevents the activation of all exceptions with configurable priority
354 - \ref __set_PRIMASK; __get_BASEPRI; __get_FAULTMASK
358 uint32_t __get_PRIMASK(void);
361 /**************************************************************************************************/
362 /** \brief Set the Priority Mask bit
364 The function sets the Priority Mask register (PRIMASK) value using the instruction \b MSR.
366 PRIMASK is a 1-bit-wide interrupt mask register. When set,
367 it blocks all interrupts apart from the non-maskable interrupt (NMI) and the hard fault exception.
368 The PRIMASK prevents activation of all exceptions with configurable priority.
370 \param [in] priMask Priority Mask
372 - =1 prevents the activation of all exceptions with configurable priority
375 - When set, PRIMASK effectively changes the current priority level to 0.
376 This is the highest programmable level.
377 - When set and a fault occurs, the hard fault handler will be executed.
378 - Useful for temporarily disabling all interrupts for timing critical tasks.
379 - Does not have the ability to mask BusFault or bypass MPU.
382 - \ref __get_PRIMASK; __set_BASEPRI; __set_FAULTMASK
386 void __set_PRIMASK(uint32_t priMask);
389 /**************************************************************************************************/
390 /** \brief Read the BASEPRI register [not for Cortex-M0, Cortex-M0+, or SC000]
392 The function returns the Base Priority Mask register (BASEPRI) using the instruction \b MRS.
394 BASEPRI defines the minimum priority for exception processing. When BASEPRI is set to a non-zero
395 value, it prevents the activation of all exceptions with the same or lower priority level as
398 \returns BASEPRI register value
401 - Not for Cortex-M0, Cortex-M0+, or SC000.
404 - \ref __set_BASEPRI; __set_BASEPRI_MAX; __get_FAULTMASK; __get_PRIMASK
408 uint32_t __get_BASEPRI(void);
411 /**************************************************************************************************/
412 /** \brief Set the BASEPRI register [not for Cortex-M0, Cortex-M0+, or SC000]
414 The function sets the Base Priority Mask register (BASEPRI) value using the instruction \b MSR.
416 BASEPRI defines the minimum priority for exception processing.
417 When BASEPRI is set to a non-zero value, it prevents the activation of all exceptions with the
418 same or lower priority level as the BASEPRI value.
420 \param [in] basePri BASEPRI value to set
423 - Not for Cortex-M0, Cortex-M0+, or SC000.
424 - Cannot be set in user state.
425 - Useful for changing the masking level or disabling the masking.
428 - \ref __get_BASEPRI; __set_BASEPRI_MAX; __set_FAULTMASK; __set_PRIMASK
432 void __set_BASEPRI(uint32_t basePri);
435 /**************************************************************************************************/
436 /** \brief Increase the BASEPRI register [not for Cortex-M0, Cortex-M0+, or SC000]
438 The function only increases the Base Priority Mask register (BASEPRI) value using the instruction \b MSR.
439 The value is set only if BASEPRI masking is disabled, or the new value increases the BASEPRI priority level.
441 BASEPRI defines the minimum priority for exception processing.
443 \param [in] basePri BASEPRI value to set
446 - Not for Cortex-M0, Cortex-M0+, or SC000.
447 - Cannot be set in user state.
448 - Useful for increasing the masking level.
449 - Has no effect when \em basePri is lower than the current value of BASEPRI.
450 - Use \ref __set_BASEPRI to lower the Base Priority Mask register.
453 - \ref __set_BASEPRI; __get_BASEPRI; __set_FAULTMASK; __set_PRIMASK
457 void __set_BASEPRI_MAX(uint32_t basePri);
460 /**************************************************************************************************/
461 /** \brief Read the FAULTMASK register [not for Cortex-M0, Cortex-M0+, or SC000]
463 The function reads the Fault Mask register (FAULTMASK) value using the instruction \b MRS.
465 FAULTMASK prevents activation of all exceptions except for the Non-Maskable Interrupt (NMI).
467 \returns FAULTMASK register value
470 - not for Cortex-M0, Cortex-M0+, or SC000.
471 - Is cleared automatically upon exiting the exception handler, except when returning
472 from the NMI handler.
475 - \ref __set_FAULTMASK; __get_BASEPRI; __get_PRIMASK
478 uint32_t __get_FAULTMASK(void);
481 /**************************************************************************************************/
482 /** \brief Set the FAULTMASK register [not for Cortex-M0, Cortex-M0+, or SC000]
484 The function sets the Fault Mask register (FAULTMASK) value using the instruction \b MSR.
486 FAULTMASK prevents activation of all exceptions except for Non-Maskable Interrupt (NMI).
487 FAULTMASK can be used to escalate a configurable fault handler (BusFault, usage fault, or
488 memory management fault) to hard fault level without invoking a hard fault. This allows the
489 fault handler to pretend to be the hard fault handler, with the ability to:
490 -# <b>Mask BusFault</b> by setting the BFHFNMIGN in the Configuration Control register.
491 It can be used to test the bus system without causing a lockup.
492 -# <b>Bypass the MPU</b>, allowing accessing the MPU protected memory location without
493 reprogramming the MPU to just carry out a few transfers for fixing faults.
495 \param [in] faultMask FAULTMASK register value to set
498 - not for Cortex-M0, Cortex-M0+, or SC000.
499 - Is cleared automatically upon exiting the exception handler, except when returning
500 from the NMI handler.
501 - When set, it changes the effective current priority level to -1, so that even the hard
502 fault handler is blocked.
503 - Can be used by fault handlers to change their priority to -1 to have access to some
504 features for hard fault exceptions (see above).
505 - When set, lockups can still be caused by incorrect or undefined instructions, or by using
506 SVC in the wrong priority level.
509 - \ref __get_FAULTMASK; __set_BASEPRI; __set_PRIMASK
512 void __set_FAULTMASK(uint32_t faultMask);
515 /**************************************************************************************************/
516 /** \brief Read the FPSCR register [only Cortex-M4 and Cortex-M7]
518 The function reads the Floating-Point Status Control Register (FPSCR) value.
520 FPSCR provides all necessary User level controls of the floating-point system.
523 - FPSCR register value, when __FPU_PRESENT=1
524 - =0, when __FPU_PRESENT=0
527 - Only for Cortex-M4 and Cortex-M7.
534 uint32_t __get_FPSCR(void);
537 /**************************************************************************************************/
538 /** \brief Set the FPSC register [only for Cortex-M4 and Cortex-M7]
540 The function sets the Floating-Point Status Control Register (FPSCR) value.
542 FPSCR provides all necessary User level control of the floating-point system.
544 - \b N (FPSC[31]) (Negative flag)
545 - =1 The instruction result has a negative value (when interpreted as signed integer).
546 - =0 The instruction result has a positive value or equal zero.
548 - \b Z (FPSC[30]) (Zero flag)
549 - =1 The instruction result is zero. Or, after a compare instruction, when the two values
552 - \b C (FPSC[29]) (Carry or borrow flag)
553 - =1 For unsigned additions, if an unsigned overflow occurred.
554 - =<i>inverse of borrow output status</i> For unsigned subtract operations.
556 - \b V (FPSC[28]) (Overflow flag)
557 - =1 A signed overflow occurred (for signed additions or subtractions).
559 - \b AHP (FPSC[26]) (Alternative half-precision flag)
560 - =1 Alternative half-precision format selected.
561 - =0 IEEE half-precision format selected.
563 - \b DN (FPSC[25]) (Default NaN mode control flag)
564 - =1 Any operation involving one or more NaNs returns the Default NaN.
565 - =0 NaN operands propagate through to the output of a floating-point operation.
567 - \b FZ (FPSC[24]) (Flush-to-zero mode control flag)
568 - =1 Flush-to-zero mode enabled.
569 - =0 Flush-to-zero mode disabled. Behavior of the floating-point system is fully
570 compliant with the IEEE 754 standard.
572 - \b RMode (FPSC[23:22]) (Rounding Mode control flags)
573 - =0b00 Round to Nearest (RN) mode.
574 - =0b01 Round towards Plus Infinity (RP) mode.
575 - =0b10 Round towards Minus Infinity (RM) mode.
576 - =0b11 Round towards Zero (RZ) mode.
577 - The specified rounding mode is used by almost all floating-point instructions.
579 - \b IDC (FPSC[7]) (Input Denormal cumulative exception flags)
580 - See Cumulative exception bits (FPSC[4:0]).
582 - \b IXC (FPSC[4]) (Inexact cumulative exception flag)
583 - =1 Exception occurred.
584 - =0 Value has to be set explicitly.
585 - Flag is not cleared automatically.
587 - \b UFC (FPSC[3]) (Underflow cumulative exception flag)
588 - =1 Exception occurred.
589 - =0 Value has to be set explicitly.
590 - Flag is not cleared automatically.
592 - \b OFC (FPSC[2]) (Overflow cumulative exception flag)
593 - =1 Exception occurred.
594 - =0 Value has to be set explicitly.
595 - Flag is not cleared automatically.
597 - \b DZC (FPSC[1]) (Division by Zero cumulative exception flag)
598 - =1 Exception occurred.
599 - =0 Value has to be set explicitly.
600 - Flag is not cleared automatically.
602 - \b IOC (FPSC[0]) (Invalid Operation cumulative exception flag)
603 - =1 Exception occurred.
604 - =0 Value has to be set explicitly.
605 - Flag is not cleared automatically.
607 \param [in] fpscr FPSCR value to set
610 - Only for Cortex-M4 and Cortex-M7.
611 - The variable \b __FPU_PRESENT has to be set to 1.
617 void __set_FPSCR(uint32_t fpscr);
620 /**************************************************************************************************/
621 /** \brief Globally enables interrupts and configurable fault handlers
623 The function enables interrupts and all configurable fault handlers by clearing PRIMASK.
624 The function uses the instruction <b>CPSIE i</b>.
627 - Can be executed in privileged mode only.
630 - \ref __disable_irq; __set_BASEPRI; __set_CONTROL; __set_PRIMASK
632 void __enable_irq(void);
635 /**************************************************************************************************/
636 /** \brief Globally disables interrupts and configurable fault handlers
638 The function disables interrupts and all configurable fault handlers by setting PRIMASK.
639 The function uses the instruction <b>CPSID i</b>.
642 - Can be executed in privileged mode only.
643 - An interrupt can enter pending state even if it is disabled. Disabling an interrupt
644 only prevents the processor from taking that interrupt.
647 - \ref __enable_irq; __set_BASEPRI; __set_CONTROL; __set_PRIMASK
649 void __disable_irq(void);
652 /**************************************************************************************************/
653 /** \brief Enables interrupts and all fault handlers [not for Cortex-M0, Cortex-M0+, or SC000]
655 The function enables interrupts and all fault handlers by clearing FAULTMASK.
656 The function uses the instruction <b>CPSIE f</b>.
659 - not for Cortex-M0, Cortex-M0+, or SC000.
660 - Can be executed in privileged mode only.
663 - \ref __disable_fault_irq; __set_BASEPRI; __set_CONTROL; __set_FAULTMASK
665 void __enable_fault_irq(void);
668 /**************************************************************************************************/
669 /** \brief Disables interrupts and all fault handlers [not for Cortex-M0, Cortex-M0+, or SC000]
671 The function disables interrupts and all fault handlers by setting FAULTMASK.
672 The function uses the instruction <b>CPSID f</b>.
675 - not for Cortex-M0, Cortex-M0+, or SC000.
676 - Can be executed in privileged mode only.
677 - An interrupt can enter pending state even if it is disabled. Disabling an interrupt
678 only prevents the processor from taking that interrupt.
681 - \ref __enable_fault_irq; __set_BASEPRI; __set_CONTROL; __set_FAULTMASK
683 void __disable_fault_irq(void);
690 \brief Get Process Stack Pointer Limit
691 Devices without Armv8-M Main Extensions (i.e. Cortex-M23) lack the non-secure
692 Stack Pointer Limit register hence zero is returned always in non-secure
695 \details Returns the current value of the Process Stack Pointer Limit (PSPLIM).
696 \return PSPLIM Register value
697 \note Only available for Armv8-M Architecture.
699 uint32_t __get_PSPLIM(void);
702 \brief Set Process Stack Pointer Limit
703 Devices without Armv8-M Main Extensions (i.e. Cortex-M23) lack the non-secure
704 Stack Pointer Limit register hence the write is silently ignored in non-secure
707 \details Assigns the given value to the Process Stack Pointer Limit (PSPLIM).
708 \param [in] ProcStackPtrLimit Process Stack Pointer Limit value to set
709 \note Only available for Armv8-M Architecture.
711 void __set_PSPLIM(uint32_t ProcStackPtrLimit);
714 \brief Get Main Stack Pointer Limit
715 Devices without Armv8-M Main Extensions (i.e. Cortex-M23) lack the non-secure
716 Stack Pointer Limit register hence zero is returned always in non-secure
719 \details Returns the current value of the Main Stack Pointer Limit (MSPLIM).
720 \return MSPLIM Register value
721 \note Only available for Armv8-M Architecture.
723 uint32_t __get_MSPLIM(void);
726 \brief Set Main Stack Pointer Limit
727 Devices without Armv8-M Main Extensions (i.e. Cortex-M23) lack the non-secure
728 Stack Pointer Limit register hence the write is silently ignored in non-secure
731 \details Assigns the given value to the Main Stack Pointer Limit (MSPLIM).
732 \param [in] MainStackPtrLimit Main Stack Pointer Limit value to set
733 \note Only available for Armv8-M Architecture.
735 __set_MSPLIM(uint32_t MainStackPtrLimit);
741 /** @} */ /** end of Core_Register_gr **/