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ADuC7126 serial download problem

We have several boards using the  ADuC7126 (Uart downlod) and the ARMWSD program indicates (always) verification error.

The oscilloscope (AC) shows a pulse of 700useg on the LVDD pin, about 120mv. This signal indicates a problem with the part or a problem with the bords layout?



  • Hi, Karl

    Thank you very much for your prompt answer. I verified the power supply and the voltage and current capability is ok, w/o noise or pulses on IOVDDx.

    The problem (the same on several parts ) is the voltage applied on IOVDD. Basically the power suply is 3v3, but the CI's tested only program and verify the flash with 2,85 v max, any value above the mentioned reports verify error

    Please, this problem is a defective part or maybe a fake component?

    I used a laboratory power supply and the GND and IOVDD voltage near the AduC.

  • In the ARMWSD, it should be able to detect the component correctly. 

    Have you also checked the voltage at the LVDD pin, when the supply voltage is below 2.85V and above 2.85V?

    You can also try checking the watchdog timer, the verification could fail, if it takes to long to download the program.

  • The ARMWSD detect the ADuC7126 correctly.

    I verified the voltage on LVDD with several values of IOVDD.

    First LVDD value is normal mode, the second one (LVDD prog) is programming mode enabled.

    IOVDD=3.3 vdc  LVDD: 2.61 vdc     LVDD prog: 2.48-2.49 vdc program error

    IOVDD=3.0 vdc  LVDD: 2.61 vdc     LVDD prog: 2.54 vdc program error

    IOVDD-2.95 vdc LVDD: 2.60           LVDD prog: 2.56 vdc program error

    IOVDD=2.90 vdc LVDD: 2.60          LVDD prog: 2.57 vdc program error

    IOVDD=2.85 vdc LVDD=2.60          LVDD prog= 2.60 vdc program ok

    Pulse on LVDD of 100mv and decresing with IOVDD between 3.3 vdc and 2.90 vdc 

    No pulse with IOVDD of 2.85 vdc

    Pleas, clarify the watch dog timer problem, I didn´t understand the point.


  • The LVDD is the supply to the core logic which requires 2.6V.

    Is there an external compensation capacitor across the LVDD pin and ground? It is recommended to connect a capacitor of 0.47µF as close as possible to these pins as shown below..

    It is also recommended to use excellent power supply decoupling on IOVDD. This helps improve the line regulation performance which is generating the 2.6V for the core logic.

    I was thinking the verification could fail if the checksum is not received by the WSD in time, so we can try monitoring the watchdog timer. However the problems seems to be more on the supply voltage to the core logic.

  • The 0.47uF is connected to pin 22 and 21 of the ADuC7126. The value of the capacitor was checked and is ok.

    The power supply is a digital control  DC Power Supply and the voltage is clean. I added more power supply decoupling on IOVDD, the original circuit uses 10uF and 0.1 uF (pins 23-48-68 of the ADuC7126), but the problem is the same. The program is running ok with 3.3 vdc on IOVDD, only to programming the voltage must be 2.85 v.

    When the voltage is 3.3 v the ARMWSD download and verifying bar is not continuous (advance and stop),when the IOVDD is 2.85 v the bar advances continuously.

  • Is there anything connected to the LVDD pin aside from the capacitor? Can you also check if something might be shorted to the pin?

  • Karl, I've checked the LVDD pin and the only one connection is the 0.47uF cap. Please take a look to the PCB image, the pin 22 (LVDD) is only connected to the cap of 0.47 uF (ceramic multilayer) C20.

  • Your right Daniel, there seems to be nothing connected to the LVDD except the capacitor.

    Can you try measuring the IOVDD when programming to the part? Also, what is the current setting used for the supply?

    You mentioned that you have several boards using the ADuC7126. Have you tried measuring the IOVDD and LVDD pins in the other units?

    For the ARMWSD, are you experiencing any issues with the mass erase command when using more than 2.85V for the IOVDD? Can you also check if there is an error when setting the ARMWSD to program only, not including the verify command?

  • IOVDD is stable during programming. The another parts have the same behavior of the mentioned part, only program and verify with IOVDD of 2.85 vdc.

    The LVD voltage is similar in value with the first one tested.

    With 3.3 vdc the mass erase is ok, no error notified.

    Selecting only program with IOVDD of 3.3 vdc (not verify) the error is the same (the progress bar delays too much and is not 'moving' continuously).

    Verification fails using 3,3 vdc or 2.85 vdc, after programming the part with IOVDD of 3.3 vdc.

  • Hi Daniel,

    Can you send the board schematic you are using here or message it to me? Can you also send the HEX file or user code you are trying to download to the ADuC7126?

  • This question has been closed since there has been no further response. If you have an inquiry about this topic, please post a new question in the applicable product forum.

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