iMX RT 1064 Processors and CPU clock rate

[Keith4DSmith]

In the data sheet for iMX RT 1064 processors there is a wide range of available CPU clock rates.

400, 500/528, 600, 700, 800, and 1000mHz

It is my understanding that the CPU clock rate is set by a multiplier of PLL1 of the clock system. 22x = 528, 25x = 600, etc.

Am I correct?

I am using the NXP SDK Board_ConfigMPU(), Board_InitBootPins(), and Boot_InitBootClock() functions as part of startup.

I have tried to find information in the iMX reference manual on how to detect and set the CPU clock, but have failed.

How is the CPU clock rate set?

If I have firmware running on different clock rate processors, how does the firmware detect the differences and set the CPU clock?

[mjbcswitzerland]

Hi

There is a practical clocking guide at
https://www.utasker.com/docs/iMX/i.MX_RT_1064_uTasker.pdf
which may help.
Much is the same as the 1021 - https://www.utasker.com/docs/iMX/i.MX_RT_1021_uTasker.pdf and the 1064 document mainly only explains the differences from the 1021 one.

Regards

Mark
[uTasker project developer for Kinetis and i.MX RT]

[Keith4DSmith]

Thank you for the links to very detailed description of iMX RT 10xx clocks.

[jeremyzhou]

Hi Keith Smith,

Thank you for your interest in NXP Semiconductor products and
for the opportunity to serve you.
1) Am I correct?
-- Yes.
2) How is the CPU clock rate set?
-- In the SDK library, it provides a variety of APIs to do that job, in addition, you can use the MCUXpresso Config Tools to do it.
3) If I have firmware running on different clock rate processors, how does the firmware detect the differences and set the CPU clock?
-- In the SDK library, it provides the CLOCK_GetFreq(clock_name_t name) to get the clock frequency for a specific clock.

/*!
 * brief Gets the clock frequency for a specific clock name.
 *
 * This function checks the current clock configurations and then calculates
 * the clock frequency for a specific clock name defined in clock_name_t.
 *
 * param clockName Clock names defined in clock_name_t
 * return Clock frequency value in hertz
 */
uint32_t CLOCK_GetFreq(clock_name_t name)
{
    uint32_t freq;

    switch (name)
    {
        case kCLOCK_CpuClk:
        case kCLOCK_AhbClk:
            freq = CLOCK_GetAhbFreq();
            break;

        case kCLOCK_SemcClk:
            freq = CLOCK_GetSemcFreq();
            break;

        case kCLOCK_IpgClk:
            freq = CLOCK_GetIpgFreq();
            break;

        case kCLOCK_PerClk:
            freq = CLOCK_GetPerClkFreq();
            break;

        case kCLOCK_OscClk:
            freq = CLOCK_GetOscFreq();
            break;
        case kCLOCK_RtcClk:
            freq = CLOCK_GetRtcFreq();
            break;
        case kCLOCK_ArmPllClk:
            freq = CLOCK_GetPllFreq(kCLOCK_PllArm);
            break;
        case kCLOCK_Usb1PllClk:
            freq = CLOCK_GetPllFreq(kCLOCK_PllUsb1);
            break;
        case kCLOCK_Usb1PllPfd0Clk:
            freq = CLOCK_GetUsb1PfdFreq(kCLOCK_Pfd0);
            break;
        case kCLOCK_Usb1PllPfd1Clk:
            freq = CLOCK_GetUsb1PfdFreq(kCLOCK_Pfd1);
            break;
        case kCLOCK_Usb1PllPfd2Clk:
            freq = CLOCK_GetUsb1PfdFreq(kCLOCK_Pfd2);
            break;
        case kCLOCK_Usb1PllPfd3Clk:
            freq = CLOCK_GetUsb1PfdFreq(kCLOCK_Pfd3);
            break;
        case kCLOCK_Usb2PllClk:
            freq = CLOCK_GetPllFreq(kCLOCK_PllUsb2);
            break;
        case kCLOCK_SysPllClk:
            freq = CLOCK_GetPllFreq(kCLOCK_PllSys);
            break;
        case kCLOCK_SysPllPfd0Clk:
            freq = CLOCK_GetSysPfdFreq(kCLOCK_Pfd0);
            break;
        case kCLOCK_SysPllPfd1Clk:
            freq = CLOCK_GetSysPfdFreq(kCLOCK_Pfd1);
            break;
        case kCLOCK_SysPllPfd2Clk:
            freq = CLOCK_GetSysPfdFreq(kCLOCK_Pfd2);
            break;
        case kCLOCK_SysPllPfd3Clk:
            freq = CLOCK_GetSysPfdFreq(kCLOCK_Pfd3);
            break;
        case kCLOCK_EnetPll0Clk:
            freq = CLOCK_GetPllFreq(kCLOCK_PllEnet);
            break;
        case kCLOCK_EnetPll1Clk:
            freq = CLOCK_GetPllFreq(kCLOCK_PllEnet25M);
            break;
        case kCLOCK_AudioPllClk:
            freq = CLOCK_GetPllFreq(kCLOCK_PllAudio);
            break;
        case kCLOCK_VideoPllClk:
            freq = CLOCK_GetPllFreq(kCLOCK_PllVideo);
            break;
        default:
            freq = 0U;
            break;
    }

    return freq;
}‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Have a great day,
TIC

-------------------------------------------------------------------------------
Note:
- If this post answers your question, please click the "Mark Correct" button. Thank you!

- We are following threads for 7 weeks after the last post, later replies are ignored
Please open a new thread and refer to the closed one, if you have a related question at a later point in time.
-------------------------------------------------------------------------------

[Keith4DSmith]

Thank you for the SDK reference to CLOCK_GetFreq(). It is in the file fsl_clock.<c,h>.

I have looked at the Mex Config tool to see the clock diagram. 

The ARM PLL1 appears to be locked. The ARM_PODF has a list of values from 1 to 8, thus changing the CPU clock rate from 1200/1 to 1200/8. This can be further divided by AHB_PODF from 1 to 8.

The iMX 1064 CPU Clock frequencies available are defined by this chart

To change the frequency to other than 400mHz it appears that the PRE_PERIPH_CLK_SEL has to be changed to PLL2_MAIN_CLK, which results in 528mHz.

I have 2 questions:

1 - What are the combinations of clock settings that provide the other listed frequencies?

2 - Is there a register or SDK function to obtain the specific MCU configuration as shown above?

[jeremyzhou]

Hi Keith Smith

Thanks for your reply.
1 - What are the combinations of clock settings that provide the other listed frequencies?
-- In my opinion, the combinations are too many to list, and various combinations can generate the same clock
2 - Is there a register or SDK function to obtain the specific MCU configuration as shown above?
- No, I'm afraid not.
Note: the above-listed frequency means the maximum frequency that the i.MX RT can run-up to.

Have a great day,
TIC

-------------------------------------------------------------------------------
Note:
- If this post answers your question, please click the "Mark Correct" button. Thank you!

- We are following threads for 7 weeks after the last post, later replies are ignored
Please open a new thread and refer to the closed one, if you have a related question at a later point in time.
-------------------------------------------------------------------------------