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<title>CMSIS Changes</title>
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<h1>Changes to CMSIS version V1.20</h1>
<hr>
<h2>1. Removed CMSIS Middelware packages</h2>
<p>
CMSIS Middleware is on hold from ARM side until a agreement between all CMSIS partners is found.
</p>
<h2>2. SystemFrequency renamed to SystemCoreClock</h2>
<p>
The variable name <strong>SystemCoreClock</strong> is more precise than <strong>SystemFrequency</strong>
because the variable holds the clock value at which the core is running.
</p>
<h2>3. Changed startup concept</h2>
<p>
The old startup concept (calling SystemInit_ExtMemCtl from startup file and calling SystemInit
from main) has the weakness that it does not work for controllers which need a already
configuerd clock system to configure the external memory controller.
</p>
<h3>Changed startup concept</h3>
<ul>
<li>
SystemInit() is called from startup file before <strong>premain</strong>.
</li>
<li>
<strong>SystemInit()</strong> configures the clock system and also configures
an existing external memory controller.
</li>
<li>
<strong>SystemInit()</strong> must not use global variables.
</li>
<li>
<strong>SystemCoreClock</strong> is initialized with a correct predefined value.
</li>
<li>
Additional function <strong>void SystemCoreClockUpdate (void)</strong> is provided.<br>
<strong>SystemCoreClockUpdate()</strong> updates the variable <strong>SystemCoreClock</strong>
and must be called whenever the core clock is changed.<br>
<strong>SystemCoreClockUpdate()</strong> evaluates the clock register settings and calculates
the current core clock.
</li>
</ul>
<h2>4. Advanced Debug Functions</h2>
<p>
ITM communication channel is only capable for OUT direction. To allow also communication for
IN direction a simple concept is provided.
</p>
<ul>
<li>
Global variable <strong>volatile int ITM_RxBuffer</strong> used for IN data.
</li>
<li>
Function <strong>int ITM_CheckChar (void)</strong> checks if a new character is available.
</li>
<li>
Function <strong>int ITM_ReceiveChar (void)</strong> retrieves the new character.
</li>
</ul>
<p>
For detailed explanation see file <strong>CMSIS debug support.htm</strong>.
</p>
<h2>5. Core Register Bit Definitions</h2>
<p>
Files core_cm3.h and core_cm0.h contain now bit definitions for Core Registers. The name for the
defines correspond with the Cortex-M Technical Reference Manual.
</p>
<p>
e.g. SysTick structure with bit definitions
</p>
<pre>
/** @addtogroup CMSIS_CM3_SysTick CMSIS CM3 SysTick
memory mapped structure for SysTick
@{
*/
typedef struct
{
__IO uint32_t CTRL; /*!< Offset: 0x00 SysTick Control and Status Register */
__IO uint32_t LOAD; /*!< Offset: 0x04 SysTick Reload Value Register */
__IO uint32_t VAL; /*!< Offset: 0x08 SysTick Current Value Register */
__I uint32_t CALIB; /*!< Offset: 0x0C SysTick Calibration Register */
} SysTick_Type;
/* SysTick Control / Status Register Definitions */
#define SysTick_CTRL_COUNTFLAG_Pos 16 /*!< SysTick CTRL: COUNTFLAG Position */
#define SysTick_CTRL_COUNTFLAG_Msk (1ul << SysTick_CTRL_COUNTFLAG_Pos) /*!< SysTick CTRL: COUNTFLAG Mask */
#define SysTick_CTRL_CLKSOURCE_Pos 2 /*!< SysTick CTRL: CLKSOURCE Position */
#define SysTick_CTRL_CLKSOURCE_Msk (1ul << SysTick_CTRL_CLKSOURCE_Pos) /*!< SysTick CTRL: CLKSOURCE Mask */
#define SysTick_CTRL_TICKINT_Pos 1 /*!< SysTick CTRL: TICKINT Position */
#define SysTick_CTRL_TICKINT_Msk (1ul << SysTick_CTRL_TICKINT_Pos) /*!< SysTick CTRL: TICKINT Mask */
#define SysTick_CTRL_ENABLE_Pos 0 /*!< SysTick CTRL: ENABLE Position */
#define SysTick_CTRL_ENABLE_Msk (1ul << SysTick_CTRL_ENABLE_Pos) /*!< SysTick CTRL: ENABLE Mask */
/* SysTick Reload Register Definitions */
#define SysTick_LOAD_RELOAD_Pos 0 /*!< SysTick LOAD: RELOAD Position */
#define SysTick_LOAD_RELOAD_Msk (0xFFFFFFul << SysTick_LOAD_RELOAD_Pos) /*!< SysTick LOAD: RELOAD Mask */
/* SysTick Current Register Definitions */
#define SysTick_VAL_CURRENT_Pos 0 /*!< SysTick VAL: CURRENT Position */
#define SysTick_VAL_CURRENT_Msk (0xFFFFFFul << SysTick_VAL_CURRENT_Pos) /*!< SysTick VAL: CURRENT Mask */
/* SysTick Calibration Register Definitions */
#define SysTick_CALIB_NOREF_Pos 31 /*!< SysTick CALIB: NOREF Position */
#define SysTick_CALIB_NOREF_Msk (1ul << SysTick_CALIB_NOREF_Pos) /*!< SysTick CALIB: NOREF Mask */
#define SysTick_CALIB_SKEW_Pos 30 /*!< SysTick CALIB: SKEW Position */
#define SysTick_CALIB_SKEW_Msk (1ul << SysTick_CALIB_SKEW_Pos) /*!< SysTick CALIB: SKEW Mask */
#define SysTick_CALIB_TENMS_Pos 0 /*!< SysTick CALIB: TENMS Position */
#define SysTick_CALIB_TENMS_Msk (0xFFFFFFul << SysTick_VAL_CURRENT_Pos) /*!< SysTick CALIB: TENMS Mask */
/*@}*/ /* end of group CMSIS_CM3_SysTick */</pre>
<h2>7. DoxyGen Tags</h2>
<p>
DoxyGen tags in files core_cm3.[c,h] and core_cm0.[c,h] are reworked to create proper documentation
using DoxyGen.
</p>
<h2>8. Folder Structure</h2>
<p>
The folder structure is changed to differentiate the single support packages.
</p>
<ul>
<li>CM0</li>
<li>CM3
<ul>
<li>CoreSupport</li>
<li>DeviceSupport</li>
<ul>
<li>Vendor
<ul>
<li>Device
<ul>
<li>Startup
<ul>
<li>Toolchain</li>
<li>Toolchain</li>
<li>...</li>
</ul>
</li>
</ul>
</li>
<li>Device</li>
<li>...</li>
</ul>
</li>
<li>Vendor</li>
<li>...</li>
</ul>
</li>
<li>Example
<ul>
<li>Toolchain
<ul>
<li>Device</li>
<li>Device</li>
<li>...</li>
</ul>
</li>
<li>Toolchain</li>
<li>...</li>
</ul>
</li>
</ul>
</li>
<li>Documentation</li>
</ul>
<h2>9. Open Points</h2>
<p>
Following points need to be clarified and solved:
</p>
<ul>
<li>
<p>
Equivalent C and Assembler startup files.
</p>
<p>
Is there a need for having C startup files although assembler startup files are
very efficient and do not need to be changed?
<p/>
</li>
<li>
<p>
Placing of HEAP in external RAM.
</p>
<p>
It must be possible to place HEAP in external RAM if the device supports an
external memory controller.
</p>
</li>
<li>
<p>
Placing of STACK /HEAP.
</p>
<p>
STACK should always be placed at the end of internal RAM.
</p>
<p>
If HEAP is placed in internal RAM than it should be placed after RW ZI section.
</p>
</li>
<li>
<p>
Removing core_cm3.c and core_cm0.c.
</p>
<p>
On a long term the functions in core_cm3.c and core_cm0.c must be replaced with
appropriate compiler intrinsics.
</p>
</li>
</ul>
<h2>10. Limitations</h2>
<p>
The following limitations are not covered with the current CMSIS version:
</p>
<ul>
<li>
No <strong>C startup files</strong> for ARM toolchain are provided.
</li>
<li>
No <strong>C startup files</strong> for GNU toolchain are provided.
</li>
<li>
No <strong>C startup files</strong> for IAR toolchain are provided.
</li>
<li>
No <strong>Tasking</strong> projects are provided yet.
</li>
</ul>