Good Idea
thanks
B.T.W. for more precision use since 64bit = 500 000 years
#define FRTimerToMs(A) (((unsigned long long) A) * 100ULL / 98304ULL)
#define MsToFRTimer(A) (((unsigned long long) A) * 98304ULL / 100ULL)
Daniel
--- In Curtis Monroe <> wrote:
>
> What if you read twice, and compared the high byte of each read. If the
> high byte matches you know you know the last time read is valid. If the
> high byte does not match you need to do it again.
>
>
> -Curtis.
>
>
>
>
>
> On Mon, 2005-06-27 at 15:50, danjperron wrote:
> > I create an extended 64 bit version of the free running timer.
> >
> >
> > But if I want to use it into some threads, I need to ensure that 2
> > threads reading tc4 will read the correct values;
> >
> > No process interrupts the reading of the low 32 bits tc4 and the
> > high 32 bits tc4 sequence. I just don't want a thread reading tc4 at
> > the same time than an other one reading the high 32 bits.
> >
> >
> > check my routine , (inspire from Jesse Off ,messages #10), GetFRTime()
> >
> >
> > ////// FreeRunningTimer.c
> >
> > #include<stdlib.h>
> > #include<unistd.h>
> > #include<sys/types.h>
> > #include<sys/mman.h>
> > #include<stdio.h>
> > #include<fcntl.h>
> >
> > #include "FreeRunningTimer.h"
> >
> >
> > int FRTimerHandle=-1;
> >
> > unsigned char *FRTimerBase=NULL;
> > unsigned long *FRTimerLo=NULL;
> > unsigned long *FRTimerHi=NULL;
> >
> > unsigned long FRTimerExtHi=0; // use to go behond 40 bit (extended)
> >
> >
> >
> > /* InitFRTimer
> > * map physical address
> > * return 0 if we can't mapped
> > * return 1 if everything ok
> > */
> >
> > int InitFRTimer(void)
> > {
> > FRTimerHandle= open("/dev/mem",O_RDWR);
> > if(FRTimerHandle<0) return(0);
> > FRTimerBase =
> >
mmap(0,getpagesize(),PROT_WRITE|PROT_READ,MAP_SHARED,FRTimerHandle,0x80810000UL);
> > if(FRTimerBase == NULL)
> > {
> > CloseFRTimer();
> > return(0);
> > }
> > FRTimerLo= (unsigned long *) (FRTimerBase + 0x60UL); // get
> > Least
> > significant long
> >
> > FRTimerHi= (unsigned long *) (FRTimerBase + 0x64UL); // get
> > Most
> > significant long
> >
> > *FRTimerHi=0x100; // start Timer
> > return(1);
> > }
> >
> >
> > /* CloseFRTimer
> > * release map of physical address
> > */
> >
> > void CloseFRTimer(void)
> > {
> >
> > if(FRTimerHandle>=0)
> > {
> > if(FRTimerBase)
> > munmap(FRTimerBase,getpagesize());
> > close(FRTimerHandle);
> > }
> > FRTimerHandle=-1;
> > FRTimerBase=NULL;
> > FRTimerLo=NULL;
> > FRTimerHi=NULL;
> > }
> >
> > /* ResetFRTimer
> > * Reset and enable Free running timer
> > */
> > void ResetFRTimer(void)
> > {
> > *FRTimerHi= 0;
> > *FRTimerHi= 0x100; // enable free running Timer
> > FRTimerExtHi=0; // reset extended bit
> > }
> >
> >
> > /* GetFRTimer
> > * return current free running timer value
> > */
> >
> >
> > unsigned long long GetFRTimer(void)
> > {
> > // need to be run at least once every 300 hours
> > // for the extended bit system to work!
> >
> > unsigned long long tval;
> >
> > unsigned long HiVal;
> >
> > // need to disable irq here
> > //
> > // ??????
> >
> > tval = *FRTimerLo;
> >
> >
> > HiVal= *FRTimerHi & 0xff;
> >
> > // need to enable irq here
> > //
> > // ?????
> >
> >
> >
> > if(HiVal < (FRTimerExtHi & 0xff))
> > {
> > // ok we got a wrapped Timer;
> >
> > FRTimerExtHi += 0x100; // increment bit 40
> > }
> > FRTimerExtHi &= ~0xff;
> > FRTimerExtHi |= HiVal;
> >
> > tval |= ((unsigned long long ) FRTimerExtHi) << 32;
> >
> > return(tval);
> > }
> >
> >
> >
> >
> > ////// FreeRunningTimer.h
> >
> > #ifndef FREE_RUNNING_TIMER_H
> > #define FREE_RUNNING_TIMER_H
> >
> >
> > int InitFRTimer(void);
> > void CloseFRTimer(void);
> > void ResetFRTimer(void);
> > unsigned long long GetFRTimer(void);
> >
> > #define FRTimerToMs(A) (((unsigned long long) A) / 984ULL)
> > #define MsToFRTimer(A) (((unsigned long long) A) * 984ULL)
> >
> > //#define FRTimerToMs(A) ((unsigned long long) A >> 10)
> > //#define MsToFRTimer(A) ((unsigned long long) A << 10)
> >
> > int IsFRTimerPassed(unsigned long long BaseTime,\
> > unsigned long long CurrentTime);
> > #endif
> >
> >
> >
> >
> >
> > ////A test program to check if the FRTimer works!
> >
> > #include<stdio.h>
> > #include<stdlib.h>
> > #include "freeRunningTimer.h"
> >
> >
> >
> > #define OUTPUT_ON 1
> > #define OUTPUT_OFF 0
> >
> >
> > void Output(int Value)
> > {
> > static int phy_out=0; // emulate real output
> > unsigned long long tcount;
> >
> > tcount= GetFRTimer();
> > if(phy_out==OUTPUT_ON)
> > {
> > if(!Value)
> > {
> > phy_out=OUTPUT_OFF; // emulate off
> > printf("Output OFF at %llu
> > (ms)\n",FRTimerToMs(tcount));fflush(stdout);
> > }
> > }
> > else
> > {
> > if(Value)
> > {
> >
> > phy_out=OUTPUT_ON; // emulate on
> > printf("Output ON at %llu
> > ms\n",FRTimerToMs(tcount));fflush(stdout);
> > }
> > }
> > }
> >
> >
> >
> > int main(void)
> > {
> >
> > int cycle;
> >
> > unsigned long long basecount;
> > unsigned long long currentcount;
> >
> >
> > if(!InitFRTimer())
> > {
> > printf("Unable to Map Free running Timer\n");
> > return(1);
> > }
> >
> > ResetFRTimer();
> > basecount =0;
> >
> >
> > for(cycle=0;cycle<5;cycle++)
> > {
> > printf("cycle %d\n",cycle);fflush(stdout);
> > while(1)
> > {
> > currentcount = GetFRTimer()- basecount;
> >
> >
> > if(FRTimerToMs(currentcount) < 1330ULL) // 1.33 seconds
> > Output(OUTPUT_ON);
> > else
> > Output(OUTPUT_OFF);
> >
> > if(FRTimerToMs(currentcount) > 5000ULL) // 5 seconds
> > {
> > basecount += MsToFRTimer(5000ULL); // basecount
> > to
> > next cycle
> > break;
> > }
> > }
> > }
> >
> >
> >
> > printf("Done\n");
> >
> > CloseFRTimer();
> >
> > return(0);
> > }
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > ______________________________________________________________________
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> >
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> >
> >
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