Convert from SysCtlDelay in TivaWare library to milliseconds and microseconds delay.

delay.c

/*
 * delay.c - Delay in millisecond and microsecond functions
 *
 *  Created on: Jul 7, 2014
 *      Author: Cuong T. Nguyen
 */
#include <stdint.h>
#include <stdbool.h>
#include "driverlib/sysctl.h"

void delayMs(uint32_t ui32Ms) {

	// 1 clock cycle = 1 / SysCtlClockGet() second
	// 1 SysCtlDelay = 3 clock cycle = 3 / SysCtlClockGet() second
	// 1 second = SysCtlClockGet() / 3
	// 0.001 second = 1 ms = SysCtlClockGet() / 3 / 1000
	
	SysCtlDelay(ui32Ms * (SysCtlClockGet() / 3 / 1000));
}

void delayUs(uint32_t ui32Us) {
	SysCtlDelay(ui32Us * (SysCtlClockGet() / 3 / 1000000));
}

Hi, bro. How do you know 1 SysCtlDelay = 3 clock cycle? It is not mentioned in reference manual.

It was 7 years ago so I'm not exactly sure where I got that number. A Google search for SysCtlDelay yields this document (which looks very familiar to me so highly likely I got the number from it). On page 77, it says:

SysCtlDelay() is a loop timer provided in TivaWare. The count parameter is the loop count, not the actual delay in clock cycles. Each loop is 3 CPU cycles

Hi, bro. How do you know 1 SysCtlDelay = 3 clock cycle? It is not mentioned in reference manual.

It is actually mentioned in the SysCtlDelay description in the api manual as the following "This function provides a means of generating a delay by executing a simple 3 instruction cycle
loop a given number of times. It is written in assembly to keep the loop instruction count
consistent across tool chains."