MPC5125 crystal problem

[jimmyli]

Part No.: MPC5125YVN400

Problem: MPC5125 failed to boot sometimes。

There are two points we suspect：

      1> Using exteral active oscillator (showed as below)，but we enable the interal oscillator, is it OK or having other effect？  --Needing NXP to verify !!!

     2> AD15 pin is pulled down unmeant because of  linking to exteral buffer chip when power on, then MCU is failed to boot.

    for 1>，we disable the internal oscillator, and the problem never happen again;

    for 2>，we can modify the hardware to make sure AD15 is pulled up when power on.

    Help you can help us to analyse for 1> !

    Thanks.

Notes：below is schmetic and test wave。

• oscillator design

• AD15 is pulled up by external resister

• power on wave

yellow—PORESET，blue—AD15（link to external Buffer chip, modified to GPIO after power on）

[Pavel]

If external active oscillator is used, the AD15 pin should be pulled down.

This setting switched off comparator for producing the output clock.

Check signal on output of your external active oscillator.

See the Table 6 and Note 1 in the MPC5125 Datasheet:

https://www.nxp.com/docs/en/data-sheet/MPC5125.pdf

See also the Section 4.2 in the MPC5125 Datasheet.

[jimmyli]

Hi Pavel,

      We have pulled down AD15 before power on, but the mpc5125 is still failed to boot.

      When the breakdown happenned, the AD0 and AD1 pin are OK, but the output of ipc_clk is abnormal.

      Below is the wave of signals, they seam to be fine.

      We guess maybe the mcu has some internal faults.

      Hope you to help us again.

      Thanks.

[jimmyli]

Hi Pavel,

      Thanks for your reply.

      We will check again.

[Pavel]

The TWR-MPC5125 board uses crystal oscillator.

I have tested the ADS5121 board (MPC5121 processor). The MPC5121 uses the same clock system as the MPC5125. The MPC5121 EMB_AX2 is used as RST_CONF_SYSOSCEN signal.

The ADS5121 board uses external crystal oscillator.

Attached file shows oscilloscope diagrams for PORESET and EMB_AX2 for the ADS5121 at power on.

There is low level on the RST_CONF_SYSOSCEN.

[jimmyli]

Hi Pavel,

      Thanks for your help.

      It is helpful to us.