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Function Called by Current Valure Register(SYST_CVR) with SysTick

PaulR

Hello guys,
Im trying to use the timer registers of my ARM Cortex M0 while using my pga970EVM. Unfortionally there aren't any files/Commands refering to using the 3 registers SYST_CSR, SYST_RVR, SYST_CVR. I figured out how these registers are working quite easily: SYST_CVR is set to the Reload Value which is defined by SYST_RVR. When SYST_CSR is enabled, SYST_CVR  gets lowered periodically and when reaching 0 its Value is reset to the reload Value. Normally there should be a function which is called as soon as the Current Value Register hits 0 but there is none in my generic firmware. The link provides the information I have on these registers.

Cortex-M0 Devices Generic User Guide (arm.com)

Do I have to write a function my own? If so how can i do it?
I already tried checking the CVR hitting 0 with an if-function: if(SYST_CVR==0x00000000)  but everything if this loop never got triggered.
Regards, Paul

Parents
  • 0 in reply to Ronan Synnott

    Hi Ronan,
    Yes CCS does allow me to view the register values. It does look like this.


    I am experimenting in 2 different versions of the firmware since the user guide is outdated, im switching between the version of the user guide and the newest. 
    When using the outdated version which is shown/used in the screenshot above, I am using this function:
    SYST_Config(0x0000FFFF,0x00000007);
    When using the latest version im writing directly into the register. I did that in the outdated version too to test its functionality and both  variants work completly fine

    SYST_CSR=0x00000007;
    SYST_RVR=0x0000FFFF;

    regarding the register declaration i found this:

    #define REG8(x) (*((volatile unsigned char *)(x)))
    #define REG16(x) (*((volatile unsigned short *)(x)))
    #define REG32(x) (*((volatile unsigned long *)(x)))

    /* NVIC Registers */
    #define NVIC_INT_TYPE REG32(0xE000E004)
    #define SYST_CSR REG32(0xE000E010)
    #define ST_ENABLE (1 << 0)
    #define ST_TICKINT (1 << 1)
    #define ST_CLKSOURCE (1 << 2)
    #define ST_COUNTFLAG (1 << 16)
    #define SYST_RVR REG32(0xE000E014)
    #define SYST_CVR REG32(0xE000E018)

    as far as my understanding goes all SYST_... registers are declared as volatile unsigned long.

    Setting 0x00000003 instead of 7 wont do the trick either and nothing changes at all (except the value of CSR).

    I do have breakpoints available, the code i posted in my 2nd post in this thread shows the IntDefaultHandler. According to line 46 it should get executed by the SysTimer. However i wasn't able to trigger it.
    While experimenting with different settings for the SysTimer i managed to crash my pga970 therefore it wasn't responding and held in reset. I might have reached calling the IntDefaultHandler which loops itself and could cause the crash. However when editing the IntDefaultHandler or replacing it, nothing happens again as in  the case before.

Reply
  • 0 in reply to Ronan Synnott

    Hi Ronan,
    Yes CCS does allow me to view the register values. It does look like this.


    I am experimenting in 2 different versions of the firmware since the user guide is outdated, im switching between the version of the user guide and the newest. 
    When using the outdated version which is shown/used in the screenshot above, I am using this function:
    SYST_Config(0x0000FFFF,0x00000007);
    When using the latest version im writing directly into the register. I did that in the outdated version too to test its functionality and both  variants work completly fine

    SYST_CSR=0x00000007;
    SYST_RVR=0x0000FFFF;

    regarding the register declaration i found this:

    #define REG8(x) (*((volatile unsigned char *)(x)))
    #define REG16(x) (*((volatile unsigned short *)(x)))
    #define REG32(x) (*((volatile unsigned long *)(x)))

    /* NVIC Registers */
    #define NVIC_INT_TYPE REG32(0xE000E004)
    #define SYST_CSR REG32(0xE000E010)
    #define ST_ENABLE (1 << 0)
    #define ST_TICKINT (1 << 1)
    #define ST_CLKSOURCE (1 << 2)
    #define ST_COUNTFLAG (1 << 16)
    #define SYST_RVR REG32(0xE000E014)
    #define SYST_CVR REG32(0xE000E018)

    as far as my understanding goes all SYST_... registers are declared as volatile unsigned long.

    Setting 0x00000003 instead of 7 wont do the trick either and nothing changes at all (except the value of CSR).

    I do have breakpoints available, the code i posted in my 2nd post in this thread shows the IntDefaultHandler. According to line 46 it should get executed by the SysTimer. However i wasn't able to trigger it.
    While experimenting with different settings for the SysTimer i managed to crash my pga970 therefore it wasn't responding and held in reset. I might have reached calling the IntDefaultHandler which loops itself and could cause the crash. However when editing the IntDefaultHandler or replacing it, nothing happens again as in  the case before.

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