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TMS320F28033: Logic level at Startup

jw
Expert 1190 points

Part Number: TMS320F28033

Hi after the device is programed with firmware, and  power is applied, what is logic level?

Can the GPIO be keep at a logic low  during power up, it not can you suggest a method to mask the output?

thanks

  • 0
    TI__Guru 52220 points

    Let me double check the TRM for this specific device and I will get back to you.

  • 0
    TI__Guru 52220 points

    Based on the datasheet,

    6.1.18 General-Purpose Input/Output (GPIO) Multiplexer

    Most of the peripheral signals are multiplexed with general-purpose input/output (GPIO) signals. This enables the user to use a pin as GPIO if the peripheral signal or function is not used. On reset, GPIO pins are configured as inputs. The user can individually program each pin for GPIO mode or peripheral signal mode. For specific inputs, the user can also select the number of input qualification cycles. This is to filter unwanted noise glitches. The GPIO signals can also be used to bring the device out of specific low-power modes.

    Therefor you have multiple options.

    1. Leave as is. The pins are configured as input.

    2. Add pull down resistors to the these pins.

    3. Configure as GPIO and force low.

    Depending on your application you can choose from these options.

  • 0 in reply to Nima Eskandari
    Expert 1190 points

    Hi is a 15k resistor  pull down large enough to to define the inputs, "select the number of input qualification cycles" what  does this mean and

    "GPIO signals can also be used to bring the device out of specific low-power modes"   is an example available of how this would be implemented?.

  • 0 in reply to jw
    TI__Guru 52220 points

    Yes 15K is a very reasonable resistor.

    The input qualification is a feature of the GPIO. Its basically a filter that can be enabled or disabled. Are you using the input qualification feature?

    The low-power mode GPIO is related to this,

    2.10 Low Power Modes

    This device has three clock-gating, low-power modes and a special power-gating mode. All low-power modes are entered by setting the LPMCR register and executing the IDLE instruction. More information about this instruction can be found in the TMS320C28x CPU and Instruction Set Reference Guide (SPRU430). Low-power modes should not be entered into while a flash program or erase is ongoing. The application should verify the following before entering STANDBY or HALT Mode: 1. Check the value of the GPIODAT register of the pin selected for STANDBY or HALT wake-up (GPIOLPMSEL0/1) prior to entering the Low-Power mode to ensure that the wake event has not already been asserted. 2. The LPMCR.QUALSTDBY register should be set to a value greater than the ratio of INTOSC1/PLLSYSCLK to ensure proper wake up. This is applicable to STANDBY only.