topic Re: KL02Z inconsistent SWD response in Kinetis Microcontrollers

KL02Z inconsistent SWD response

haimf — Tue, 16 Jun 2015 15:35:45 GMT

Hi,

I'm hoping for some guidance in regards to using SWD to access the FRDM-KL02Z board.

I connected 2 GPIO pins on my board to the SWDIO and SWDCLK pins on the board for SWD access to the FRDM-KL02Z board.

I was using the instructions on this forum discussion

https://community.freescale.com/thread/350691

to configure the SWD initialization sequence, and I was able to read the IDCODE and get access to the access port.

The problem I encounter is inconsistency in the board response. I am able to recreate it as follows:

Initialization sequence:

SWDCLK is set to output.
Host turns SWDIO into an output and drives it high, SWDCLK is strobed from high to low 64 times.
0x9E is sent LSb First over SWDIO by the host
0xE7 is sent LSb First over SWDIO by the host
Host turns SWDIO into an output and drives it high, SWDCLK is again strobed from high to low 64 times
SWDIO is set low and the clock is strobed once
Header to read IDCODE is formed and sent, ACK OK received, 32 bits of Data recieved, 1 parity bit received, Data is 0x0BC11477

I then, try to redo the last action- read the IDCODE many times.

After several retries (the amount of retries is inconsistent) of successful reads, I get a fault ACK- which can be 0x4 or 0x7 (which are illegal ACKs in debug port accesses), and I have to redo the init sequence in order to be able to read again.

This problem happens in all kind of read/write operations to the debug and the access ports. I used scope to get the signals coming from the board, and I see that the ACK signals are indeed faulty.

Do you have any idea, what might cause this inconsistency in the board’s response?

Many thanks,
Haim

Re: KL02Z inconsistent SWD response

miduo — Tue, 07 Jul 2015 06:32:26 GMT

Hi, Haim

Sorry for the late response. Regarding your issue, did you mean that you have used one FRDM-KL02Z to programming another FRDM-KL02Z? If I am understaning is correct, please let me know if you had effectively isolate the on-board MCU from the OpenSDA debug interface of the programmed FRDM-KL02Z? Please sent me the schematic for reivew if possible.

Re: KL02Z inconsistent SWD response

haimf — Tue, 07 Jul 2015 15:30:59 GMT

Hi Fang Li,

I have connected the FRDM-KL02Z to another board (FRDM-KL02Z) and I am using the GPIO pins on my board to toggle the SWDIO and SWDCLK pins on the KL02Z.

As I mentioned, I was able to initialize the SWD connection and get communication running between the 2 boards. The problem is, after several SWD commands (which the KL02Z returns OK ACK) I am getting a faulty ACK (0x4) from the KL02Z and I must reinitialize the SWD connection.

Can you tell what might cause this inconsistency in the board’s response?

Thanks,

Haim