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PROCESSOR-SDK-AM64X: M4F interrupt latency

Peter Budenszki
Prodigy 40 points

Part Number: PROCESSOR-SDK-AM64X
Other Parts Discussed in Thread: TMDS64EVM

Hi Support,

I have been working on a project where an M4F is connected to a display via its GPIO pins. The display requires 5MHz clock from M4F and also some sync signals and 16 bit data. So the refresh rate is 5MHz.

I am able to generate 5MHz with DMTIMER in PWM mode, and also registered an interrupt if timer expires. Unfortunately the IRQ latency is approximately 260ns (measured with oscilloscope probe, GPIO pin is set at the beginning of IRQ handler) relative to 5MHz rising edge. 

  • what is the MCU_GPIO typical latency? I mean the time elapsed between writing data to GPIO_OUT_DATA01 register and setting the pin physically,
  • what is the interrupt latency? Time between expiration of the timer and the actual entry into the ISR

Environment:

  • mcu_plus_sdk_am64x_08_06_00_43
  • MCU_TIMER_IO2 in pwm mode with 5MHz output, B8 pin
  • CCS: 12.3
  • TMDS64EVM board
  • D6 pin is observed with the probe
  • CCS project in Release mode

Peter

  • 0
    Prodigy 40 points

    Hil,

    some addition:

    the picture below is showing:

    GREEN signal is a MCU_TIMER2 PWM output at B8 pin

    YELLOW ( D6 pin, controlled my software):

    - rising edge at the entry in the void HWI_SECTION HwiP_interrupt_handler() function in HwiP_armv7m_handlers_nortos.c file

    - falling edge: end of my empty ISR function

    It takes 160ns from the TIMER2 PWM falling edge interrupt (both edges have the same behaviour) to the beginning of ISR. Maybe the TIMER2 interrupt time and the actual signal rising/falling time has quite big latency? How can I measure the real PWM interrupt relative to the actual PWM signal?

    note: GPIO pin is controller by direct register write, no built-in write function is used.

    Peter

  • 0 in reply to Peter Budenszki
    TI__Genius 12410 points

    Peter,

    Peter Budenszki said:
    what is the MCU_GPIO typical latency

    This is not a straight forward Question i can answer , It depends on the interconnect latency. Let me try to reach to the right experts and get an answer.

    In the meantime can you please help us understand what are you trying to do as a part of your application. i might be able to help you with your solution.

    Regards

    Anshu