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MKL16 SWD reset functionality

Question asked by Mads Nielsen on Sep 22, 2016
Latest reply on Sep 29, 2016 by Jorge Antonio Alcala Vazquez


I have a question regarding a Freescale MKL16Z256XXX4 that I am using in a design and firmware update. I have disabled the Reset functionality on the SWD port. By reading the document AN4835 “Production Flash Programming Best Practices for Kinetis K- and L-series MCUs” in section 4.1.1 it says that to establish SWD connection the Reset pin needs to be asserted and then communication can be established with the ARM DAP to update and read MDM-AP for status. The reference manual KL16P80M48SF4RM says in section 9 says that a reset state can be achieved by accessing the DP CTRL/STAT register. The question is, am I always guaranteed to enter a reset state of the MCU by sending commands to the ARM DAP without having the Reset pin available or is the Reset pin mandatory to guarantee prober reset and then firmware download into the MCU? What is the delay from the Reset state is requested by sending data to the MDM-AP to the MCU enters its reset state and is halted and further actions can be performed, i.e. flash erase, programming etc.?

Kind regards, Mads Nielsen