Porting MSP430F5529's intrinsic __delay_cyles() to MSP432P401R

Manh Nguyen76

Other Parts Discussed in Thread: MSP430F5529

I'm porting Pervasive Displays code for their Extension Kit, http://www.pervasivedisplays.com/kits/ext_kit, from MSP430F5529 to MSP432P401R.

MSP430 has an intrinsic __delay_cycles(). I looked for equivalent one in MSP432 but found none. Is there any ? If not what are the workarounds ?

One possible solution is use MSP432's intrinsic of sleep() and a timer but I want to avoid that because I don't want to use up the timers.

over 10 years ago

0 Chester Gillon over 10 years ago

Guru 92251 points

The TI ARM v5.2.x compiler does support a _delay_cycles() intrinsic, which I have used on other ARM devices such as a Cortex M4F Tiva device, so should work on a Cortex M4F MSP432 device.

One issue I found was that on some ARM devices was that the actual delay could be several times that requested and could change according to the code alignment - see What is its unit of number of _delay_cycles()

i.e. using _delay_cycles() can be difficult to generate a deterministic delay, even when no interrupts are occurring..

0 Brian Boorman over 10 years ago

Guru 25210 points

According to the documentation I have from the pre-announcement training last June, CCS supports the __delay_cycles() intrinsic. You need to #include "msp430dna.h"

0 Tao Cui over 10 years ago in reply to Brian Boorman

Prodigy 40 points

Thanks, but forgive me for this rookie question: where is this "msp430dna.h" file? I am not using CCS. Thanks!

0 Katie Pier over 10 years ago in reply to Tao Cui

TI__Guru 73216 points

Tao,

What compiler are you using? I think your intrinsics that you can use or need to use are going to vary with that. Do you IAR? Or maybe GCC?

-Katie

0 Tao Cui over 9 years ago in reply to Katie Pier

Prodigy 40 points

I am using CCSv6 but use GCC tool chain: GNU v4.8.4 (Linaro).

I am using GCC because it offers some features I need. But it cannot find this msp430dna.h. Do you know where it is?

Thanks!

0 DavidL over 9 years ago in reply to Tao Cui

TI__Mastermind 25045 points

Hi Tao,

We do not support this intrinsic in GNU(gcc) or IAR. So you will have to implement it yourself.

This is what I use:

#include <stdbool.h>
#include <stdint.h>
#include "driverlib.h"
#include "demo_sysctl.h"

//*****************************************************************************
//
//! Provides a small delay.
//!
//! \param ui32Count is the number of delay loop iterations to perform.
//!
//! 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.
//!
//! It is important to note that this function does NOT provide an accurate
//! timing mechanism.  Although the delay loop is 3 instruction cycles long,
//! the execution time of the loop will vary dramatically depending upon the
//! application's interrupt environment (the loop will be interrupted unless
//! run with interrupts disabled and this is generally an unwise thing to do)
//! and also the current system clock rate and flash timings (wait states and
//! the operation of the prefetch buffer affect the timing).
//!
//! For best accuracy, a system timer should be used with code either polling
//! for a particular timer value being exceeded or processing the timer
//! interrupt to determine when a particular time period has elapsed.
//!
//! \return None.
//
//*****************************************************************************
#if defined(ewarm) || defined(DOXYGEN)
void
SysCtlDelay(uint32_t ui32Count)
{
    __asm("    subs    r0, #1\n"
          "    bne.n   SysCtlDelay\n"
          "    bx      lr");
}
#endif
#if defined(codered) || defined(gcc) || defined(sourcerygxx)
void __attribute__((naked))
SysCtlDelay(uint32_t ui32Count)
{
    __asm("    subs    r0, #1\n"
          "    bne     SysCtlDelay\n"
          "    bx      lr");
}
#endif
#if defined(rvmdk) || defined(__ARMCC_VERSION)
__asm void
SysCtlDelay(uint32_t ui32Count)
{
    subs    r0, #1;
    bne     SysCtlDelay;
    bx      lr;
}
#endif
//
// For CCS implement this function in pure assembly.  This prevents the TI
// compiler from doing funny things with the optimizer.
//
#if defined(ccs)
__asm("    .sect \".text:SysCtlDelay\"\n"
      "    .clink\n"
      "    .thumbfunc SysCtlDelay\n"
      "    .thumb\n"
      "    .global SysCtlDelay\n"
      "SysCtlDelay:\n"
      "    subs r0, #1\n"
      "    bne.n SysCtlDelay\n"
      "    bx lr\n");
#endif

Best regards,

David

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Porting MSP430F5529's intrinsic __delay_cyles() to MSP432P401R