TM4C129ENCPDT: Flashing microcontroller and pins behavior control

Sahil

Part Number: TM4C129ENCPDT
Other Parts Discussed in Thread: UNIFLASH

Hi,

I want to know how to control the pins behavior while the controller is being flashed.

Assume controller is connected to some LEDs and I do not want the LEDs start blinking due to the controller being flashed.

How can i keep some of the pins behavior as LOW and some as HIGH till the controller is fully programmed.

Thank you for your help.

Regards,

Sahil

over 5 years ago

+1 Andy Peters over 5 years ago

Genius 3945 points

When you program the flash memory via JTAG, the processor is in reset, which means that the GPIO pins are configured as inputs. Their state is set by whatever might be connected to them.

As for keeping some pins low and some pins high during programming, consider a custom boot loader that sets the pins as you need them to be set while updating the program memory flash.

0 Charles Tsai over 5 years ago in reply to Andy Peters

TI__Guru**** 191886 points

Hi Andy,

Thank you for your answer. Just a little correction. The processor will be out of reset when you are programming the flash. If the processor is in reset then it can't execute the programming code. Normally, the flash programmer (e.g. CCS, Uniflash or LM flash programmer) will download programming code to RAM for the CPU to execute. The rest I agree with you.

0 Sahil over 5 years ago in reply to Charles Tsai

Expert 1585 points

Hi Thank you Andy a Charles.

Can I use TMS pin of JTAG connection ( which is usually Pulled-up to 3.3V ) as an indicator that the controller is being programmed. Here I assume the TMS remains LOW when the controller is being programmed ?

0 Charles Tsai over 5 years ago in reply to Sahil

TI__Guru**** 191886 points

Hi,

Sahil said:
Here I assume the TMS remains LOW when the controller is being programmed ?

This is not true. TMS is the test mode signal. It changes state to step into different TAP states.

0 Sahil over 5 years ago in reply to Charles Tsai

Expert 1585 points

Okay thanks.

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TM4C129ENCPDT: Flashing microcontroller and pins behavior control