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DP83848I Software Reset

Gregory Watkins
Expert 4005 points
Other Parts Discussed in Thread: DP83848I

Team,

Datasheet for DP83848I states:

"A software reset is accomplished by setting the reset bit (bit 15) of the Basic Mode Control Register (BMCR). The period from the point in time when the reset bit is set to the point in time when software reset has concluded is approximately 1us.  The software reset will reset the device such that all registers will be reset to default values and the hardware configuration values will be maintained. Software driver code must wait 3us following a software reset before allowing further serial MII operations with the DP83848I."

Current Lab testing is showing reset time is about 2.8us, is this to be expected?

Additionally, does the sowftware reset reinitialize the polarity of the LED outputs?  The description above says that the hardware configuration values will be maintained.  What are the hardware configuration values? 

  • 0
    TI__Mastermind 31600 points

    The hardware configuration values refers to the strap options.  At power up or after a hardware reset, the straps will be loaded into the device.  Once they are loaded, the straps will not be loaded based on a software reset. 

    The LED polarity is determined based on the strap configuration of the LED pins.  Therefore, a software reset should not change the polarity of the LED output driver.

    Patrick

  • 0 in reply to Patrick OFarrell
    TI__Mastermind 31600 points

    Greg,

    The information that I previously provided is not correct for the DP83848. For the DP83848, applying a software reset will cause the DP83848 to re-initialize all registers to default values and re-latch all the straps similar to a hardware reset or a power on reset. 

    Regarding the LED polarity, it is still determined by the strap configuration of the LED pins.  If the strap configuration of the LED pins has not changed, then the polarity of the LED output drivers should not change.  The main consideration here is that it is important to choose pull-up or pull-down resistors for each of the hardware configuration pins that provide fast RC time constants in order to latch-in the proper value prior to the pin transitioning to an output driver.

    I apologize for the confusion.  I was looking at this wrong and had my mistake pointed out to me after my post. 

    Patrick