Jtag Debug Disable option in LPC4367 Controller

[gauravmore]

Hi,

I am using LPC 4367 controller for one of my development. I am looking for the feature of disabling the Jtag debug feature in the controller, where it will disable it permanently.  this we require in order to release the code and product as per our policy in production.

With respect to the above feature I checked it in the data sheet of LPC4367 (UM10503) and there I found below mentioned input. Where it mention that it will be disabled and after chip rest it will be enabled.

Is it the only way or is there any other provision where we can disable the Jtag debug mode permanently. 

Awaiting reply..

Thanks

Gaurav More

[EdwinHz]

Hello @gauravmore.

Code Read Protection (CRP) is a mechanism in the LPC436x that disables access to the chip via JTAG and/or ISP. See Section 6.6 (p. 74) of the aforementioned User Manual UM10503. Table 31 describes the options that can be programmed at offset 0x2FC to enable the different CRP levels of security. As Figure 15 (p. 57) shows, if CRP is enabled, enabling debug will be skipped after a reset.

Best regards,

Edwin.

[gauravmore]

Hi Edwin,

Thanks for the reply,

I got the point. But one more query regarding  CRP enabling. In MCU Xpresso while creating the project there is an option of Enabling the CRP. Will it  preform the same operation?

Or we need to write the pattern mentioned in the datasheet at the location mentioned in it? Also in a project do we need to always write the pattern at offset 0x2FC at every power ON?

Thanks

Gaurav More

[converse]

If you use MCXUpresso, then the tools will handle the correct placement of the CRP value. See 

https://community.nxp.com/t5/LPCXpresso-IDE-FAQs/Code-Read-Protection-CRP/m-p/468962

As CRP is a value in flash, then it is always set to that value - you do not need to do anything.

However, a couple of notes:

- CRP can prevent you accessing your chip via debug, so use it carefully

- there is a small window during power-up where, in theory, it is possible to gain access to the chip via debug, even if CRP disables it. You can find some description on the internet (but not on the NXP website!)

[gauravmore]

Hi Converse,

Thanks for the reply.

I found one thing that while creating the project in MCUXpresso through the project wizard the CRP option is enable by default but still I was able to debug the code while development. 

I also want confirmation regarding the flash program. Means after enabling the CRP option still I should be able to upgrade the firmware using bootloader through IAP commands. since we need to initiate for the boot loader development.

Thanks

Gaurav More

[converse]

"You can give a man a fish, and he'll feed himself for a day. Teach a man to fish, and he can feed himself for life".

Rather than telling you exactly what to do, and you not understand how and why it works, why don't you read the manual(s) and learn how it works? The CRP mechanism is described in the LPC4300 User Manual. The MCUXpresso assistance for CRP is described in the MCUXpresso IDE User Manual (Code Read Protection section) and also by reading crp.c in your project.

[gauravmore]

Hi Converse,

Thanks for the reply. 

We did the same al the time at the back end regarding the understanding and implementing the functionality using the user manuals and on the other side also check whether we get any input that will help in case of our development.

Will be referring the manuals only for the development. Will check and let you know if any other point comes in while development,

Thanks 

Gaurav More