I Performed a clean reinstall of all tools and packages.
core_cm4.h file exists at location: C:\..\..\..\..\..\Nordic\nRF5_SDK_15.3.0_59ac345\nRF5_SDK_15.3.0_59ac345\components\toolchain\cmsis\include
added relative path to blinky project settings under C/C++ tab as \..\..\..\..\..\components\toolchain\cmsis\include and moved it to the top of the list.
added relative path to blinky project settings under Asm tab as \..\..\..\..\..\components\toolchain\cmsis\include and moved it to the top of the list.
Closed application and restarted.
The error report (below) doesn't show it even looking in this directory.
Rebuild started: Project: blinky_pca10040
*** Using Compiler 'V5.06 update 6 (build 750)', folder: 'C:\Keil_v5\ARM\ARMCC\Bin'
Rebuild target 'nrf52832_xxaa'
assembling arm_startup_nrf52.s...
compiling system_nrf52.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\modules\nrfx\mdk\system_nrf52.c: 0 warnings, 1 error
compiling main.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\main.c: 0 warnings, 1 error
compiling boards.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\components\boards\boards.c: 0 warnings, 1 error
compiling nrfx_atomic.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\modules\nrfx\soc\nrfx_atomic.c: 0 warnings, 1 error
compiling app_error.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\components\libraries\util\app_error.c: 0 warnings, 1 error
compiling app_error_handler_keil.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\components\libraries\util\app_error_handler_keil.c: 0 warnings, 1 error
compiling app_error_weak.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\components\libraries\util\app_error_weak.c: 0 warnings, 1 error
compiling app_util_platform.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\components\libraries\util\app_util_platform.c: 0 warnings, 1 error
compiling nrf_assert.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\components\libraries\util\nrf_assert.c: 0 warnings, 1 error
compiling nrf_atomic.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\components\libraries\atomic\nrf_atomic.c: 0 warnings, 1 error
compiling nrf_balloc.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\components\libraries\balloc\nrf_balloc.c: 0 warnings, 1 error
compiling nrf_fprintf.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\external\fprintf\nrf_fprintf.c: 0 warnings, 1 error
compiling nrf_memobj.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\components\libraries\memobj\nrf_memobj.c: 0 warnings, 1 error
compiling nrf_fprintf_format.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\external\fprintf\nrf_fprintf_format.c: 0 warnings, 1 error
compiling nrf_ringbuf.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\components\libraries\ringbuf\nrf_ringbuf.c: 0 warnings, 1 error
compiling nrf_strerror.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\components\libraries\strerror\nrf_strerror.c: 0 warnings, 1 error
compiling nrf_log_frontend.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\components\libraries\log\src\nrf_log_frontend.c: 0 warnings, 1 error
compiling nrf_log_str_formatter.c...
..\..\..\..\..\..\modules\nrfx\mdk\nrf52.h(150): error: #5: cannot open source input file "core_cm4.h": No such file or directory
#include "core_cm4.h" /*!< ARM Cortex-M4 processor and core peripherals */
..\..\..\..\..\..\components\libraries\log\src\nrf_log_str_formatter.c: 0 warnings, 1 error
".\_build\nrf52832_xxaa.axf" - 18 Error(s), 0 Warning(s).
Target not created.
Build Time Elapsed: 00:00:03
\components\toolchain\cmsis\include
