SPRACP6 December   2019 TMS320F2800132 , TMS320F2800133 , TMS320F2800135 , TMS320F2800137 , TMS320F2800152-Q1 , TMS320F2800153-Q1 , TMS320F2800154-Q1 , TMS320F2800155 , TMS320F2800155-Q1 , TMS320F2800156-Q1 , TMS320F2800157 , TMS320F2800157-Q1 , TMS320F280021 , TMS320F280021-Q1 , TMS320F280023 , TMS320F280023-Q1 , TMS320F280023C , TMS320F280025 , TMS320F280025-Q1 , TMS320F280025C , TMS320F280025C-Q1 , TMS320F280040-Q1 , TMS320F280040C-Q1 , TMS320F280041 , TMS320F280041-Q1 , TMS320F280041C , TMS320F280041C-Q1 , TMS320F280045 , TMS320F280048-Q1 , TMS320F280048C-Q1 , TMS320F280049 , TMS320F280049-Q1 , TMS320F280049C , TMS320F280049C-Q1

 

  1.   How to Maximize GPIO Usage in C2000 Devices
    1.     Trademarks
    2. 1 Introduction
    3. 2 Zero Pin Boot Mode Option
      1. 2.1 Weak Pull-Up Method
      2. 2.2 Zero Pin Boot Mode Method
    4. 3 cJTAG Option
    5. 4 Zero Pin Internal Oscillator Option
    6. 5 CMPSS to Save Extra GPIO for Fast Protection
    7. 6 AIO Option
    8. 7 Using the GPDACs as General Purpose Outputs
    9. 8 Optional 1.2-V Internal DCDC
    10. 9 References

4 Zero Pin Internal Oscillator Option

If using the internal oscillator as the clock source, the X2 pin can be used as a GPIO. Note that if using X2 as a GPIO, X1 has to be pulled down with a 1kΩ resistor for correct functionality.

Unlike legacy devices, the F28004x device does not require oscillator compensation since the trimming during factory testing takes care of this. Typically, the internal oscillator frequency is less than ±1% from target across voltage/temperature. However, when the lifetime of the device is taken into consideration, the frequency stability can not be guaranteed, so the maximum frequency shift will be ±3%, as shown in the Table 3.

Table 3. Internal Oscillators Characteristics

Parameter Test Conditions MIN TYP MAX UNIT
fINTOSC Frequency, INTOSC1 and INTOSC2 9.7 10 10.3 MHz
fINTOSC-STABILITY Frequency stability at room temperature 30°C, Nominal VDD ±0.1%
Frequency stability over VDD 30°C ±0.2%
Frequency stability –3% 3%
tINT0SC-ST Start-up and settling time 20 µs

Note that since timing requirements for CAN is critical, it is recommended to use an external oscillator if the CAN module is being used in the application. The required frequency tolerance for the CAN bit clock depends on the bit timing setup and network configuration, and can be as tight as 0.1%. Furthermore, the ADC has non-negligible sensitivity with the clock source. When using INTOSC as the system clock, the ADC will incur performance degradation, like lower SNR. Flash operation will also be affected, since an extra flash wait state is needed if INTOSC is used as the clock source for F28004x. For more details, see the TMS320F28004x Piccolo™ Microcontrollers Data Manual.