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31 ******************************************************************************/
32 /*****************************************************************************/
37 * This function provides a microsecond delay using the Global Timer register in
38 * the ARM Cortex A9 MP core.
41 * MODIFICATION HISTORY:
43 * Ver Who Date Changes
44 * ----- -------- -------- -----------------------------------------------
45 * 1.00a ecm/sdm 11/11/09 First release
46 * 3.07a sgd 07/05/12 Upadted micro sleep function to make use Global Timer
47 * 4.2 pkp 08/04/14 Removed unimplemented nanosleep routine as it is not
48 * possible to generate timer in nanosecond due to
49 * limited cpu frequency
52 ******************************************************************************/
53 /***************************** Include Files *********************************/
57 #include "xparameters.h"
58 #include "xil_types.h"
59 #include "xpseudo_asm.h"
60 #include "xreg_cortexa9.h"
62 /* Global Timer is always clocked at half of the CPU frequency */
63 #define COUNTS_PER_USECOND (XPAR_CPU_CORTEXA9_CORE_CLOCK_FREQ_HZ / (2U*1000000U))
65 /*****************************************************************************/
68 * This API gives a delay in microseconds
70 * @param useconds requested
72 * @return 0 if the delay can be achieved, -1 if the requested delay
77 ****************************************************************************/
78 s32 usleep(u32 useconds)
83 tEnd = tCur + (((XTime) useconds) * COUNTS_PER_USECOND);
87 } while (tCur < tEnd);