SBAA607A December   2023  – January 2024 AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1 , AM263P4 , AM263P4-Q1 , AMC1303M2520 , AMC1305L25 , AMC1306M25 , F29H850TU , F29H859TU-Q1 , TMS320F280033 , TMS320F280034 , TMS320F280034-Q1 , TMS320F280036-Q1 , TMS320F280036C-Q1 , TMS320F280037 , TMS320F280037-Q1 , TMS320F280037C , TMS320F280037C-Q1 , TMS320F280038-Q1 , TMS320F280038C-Q1 , TMS320F280039 , TMS320F280039-Q1 , TMS320F280039C , TMS320F280039C-Q1 , TMS320F280040-Q1 , TMS320F280040C-Q1 , TMS320F280041 , TMS320F280041-Q1 , TMS320F280041C , TMS320F280041C-Q1 , TMS320F280045 , TMS320F280048-Q1 , TMS320F280048C-Q1 , TMS320F280049 , TMS320F280049-Q1 , TMS320F280049C , TMS320F280049C-Q1 , TMS320F28075 , TMS320F28075-Q1 , TMS320F28076 , TMS320F28374D , TMS320F28374S , TMS320F28375D , TMS320F28375S , TMS320F28375S-Q1 , TMS320F28376D , TMS320F28376S , TMS320F28377D , TMS320F28377D-Q1 , TMS320F28377S , TMS320F28377S-Q1 , TMS320F28378D , TMS320F28378S , TMS320F28379D , TMS320F28379D-Q1 , TMS320F28379S , TMS320F28384D , TMS320F28384D-Q1 , TMS320F28384S , TMS320F28384S-Q1 , TMS320F28386D , TMS320F28386D-Q1 , TMS320F28386S , TMS320F28386S-Q1 , TMS320F28388D , TMS320F28388S , TMS320F28P650DH , TMS320F28P650DK , TMS320F28P650SH , TMS320F28P650SK , TMS320F28P659DH-Q1 , TMS320F28P659DK-Q1 , TMS320F28P659SH-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Design Challenge With Digital Interface Timing Specifications
  6. 3Design Approach With Clock Edge Delay Compensation
    1. 3.1 Clock Signal Compensation With Software Configurable Phase Delay
    2. 3.2 Clock Signal Compensation With Hardware Configurable Phase Delay
    3. 3.3 Clock Signal Compensation by Clock Return
    4. 3.4 Clock Signal Compensation by Clock Inversion at the MCU
  7. 4Test and Validation
    1. 4.1 Test Equipment and Software
    2. 4.2 Testing of Clock Signal Compensation With Software Configurable Phase Delay
      1. 4.2.1 Test Setup
      2. 4.2.2 Test Measurement Results
    3. 4.3 Testing of Clock Signal Compensation by Clock Inversion at MCU
      1. 4.3.1 Test Setup
      2. 4.3.2 Test Measurement Results
        1. 4.3.2.1 Test Result – No Clock Inversion of Clock Input at GPIO123
        2. 4.3.2.2 Test Result – Clock Inversion of Clock Input at GPIO123
    4. 4.4 Digital Interface Timing Validation by Calculation Tool
      1. 4.4.1 Digital Interface With No Compensation Method
      2. 4.4.2 Commonly Used Method - Reduction of the Clock Frequency
      3. 4.4.3 Clock Edge Compensation With Software Configurable Phase Delay
  8. 5Conclusion
  9. 6References
  10. 7Revision History

4.3.2.2 Test Result – Clock Inversion of Clock Input at GPIO123

Figure 4-7 shows the clock signal SD1_C1 which is input to GPIO123 and the phase shifted data signal SD1_D1 which is input to GPIO122. In this test setup GPIO123 is inverted by the software, as shown below.

// Set 3-sample qualifier for GPIO122 and GPIO123 and do not invert GPIO123
GPIO_SetupPinOptions(123, GPIO_INPUT, GPIO_INVERT | GPIO_QUAL3);   
GPIO_SetupPinMux(122,GPIO_MUX_CPU1,7); // MUX position 7 for SD1_D1
GPIO_SetupPinMux(123,GPIO_MUX_CPU1,7); // MUX position 7 for SD1_C1

The data SD1_D1 is now sampled by F28379D SDFM at the falling edge of SD1_C1, which corresponds to the rising edge of the inverted clock signal at GPIO123 input. The data sampled by the F28379D was always logic ‘0’, validated though output of the Sinc3 OSR64 filter = -16384 in Code Composer Studio, as shown below.

GUID-20231128-SS0I-RBW2-MFVB-XGRJPJBNCP00-low.svg Figure 4-7 Clock and Data Input Test Signals (Non-Inverted GPIO123) and Sinc3 OSR 64 Filter Output in CCS

In conclusion the method of clock signal compensation by inverting the clock input of the GPIO input in software was validated. By inverting the clock, a fixed delay of half of the clock period is added to the clock signal which can be sufficient to meet the TMS320F28379D setup and hold of minimum timings of 10 ns for the SDFM qualified GPIO (3-sample) mode 0. However, each system design needs to be checked individually if the resulting timings for setup and hold of the MCU for the SDFM qualified GPIO (3-sample) mode 0 can be met.