LPC55S28 - cannot connect debugger or enter ISP mode after disabling secure boot

[awseiger]

Hello,

I have been trying to get to the bottom of my inability to attach to a running LPC55S28 target and issue a device reset, and I tried disabling secure boot in the CFPA.

I did this and power-cycled my board, and now the MCU will not enter ISP mode, or allow my J-Link to connect. When issuing "connect" on my J-link I get the following error:

I tried running some of the debug mailbox commands outlined in the user manual, but I could not get these to complete successfully.

Thanks,

Alex

[Alice_Yang]

Same case with salesforce.

[Alice_Yang]

Hello awseiger,

If chip can't enter ISP mode, maybe chip is broken, or disabled ISP mode:

BR

Alice

[awseiger]

Alice,

Prior to power cycling the MCU, I did a full read-back of the CMPA. Word 0 in the CMPA was all zeros, so ISP mode was absolutely enabled.

Alex