To start with this, enter to the bootloader mode, if you are using openSDA hardware interface. So no any other interface is active which would block an access to the target.
I connected my jlink to it, shown error while connecting to the chip. Usually when I locked kinetis chip, at least jlink was able to connect to MCU. This time I assumed the mass erase protection bit was set. Thus I followed just simple steps find out what is the state of my core. I got lucky, the mass erase bit was not set, jlink was able to unlock the kinetis. If mass erase bit is set, it would fail. I accidentally selected KL26Z chip.
SEGGER J-Link Commander V4.76f ('?' for help)
Compiled Sep 27 2013 16:54:08
DLL version V4.76f, compiled Sep 27 2013 16:53:51
Firmware: J-Link Lite-FSL V1 compiled Jun 25 2012 16:40:07
Hardware: V1.00
S/N: 361000149
VTarget = 2.874V
Info: Could not measure total IR len. TDO is constant high.
Info: Could not measure total IR len. TDO is constant high.
No devices found on JTAG chain. Trying to find device on SWD.
Info: Found SWD-DP with ID 0x0BC11477
****** Error: Error while identifying Cortex-M core.
Info: Found SWD-DP with ID 0x0BC11477
No device found on SWD.
Failed to identify target. Trying again with slow (4 kHz) speed.
Info: Could not measure total IR len. TDO is constant high.
Info: Could not measure total IR len. TDO is constant high.
No devices found on JTAG chain. Trying to find device on SWD.
Info: Found SWD-DP with ID 0x0BC11477
****** Error: Error while identifying Cortex-M core.
Info: Found SWD-DP with ID 0x0BC11477
No device found on SWD.
J-Link>device ?
Info: Device "MKL26Z128XXX4" selected (128 KB flash, 16 KB RAM).
Reconnecting to target...
Info: Could not measure total IR len. TDO is constant high.
Info: Could not measure total IR len. TDO is constant high.
J-Link>unlock kinetis
Unlocking device...O.K.J-Link>SWDReadAP 0x1000000
Read AP register 16777216 = 0x00000000
J-Link>SWDReadAP 0x1000000
Read AP register 16777216 = 0x00000031
J-Link>erase
Info: Found SWD-DP with ID 0x0BC11477
Info: Found SWD-DP with ID 0x0BC11477
Info: Found Cortex-M0 r0p0, Little endian.
Info: FPUnit: 2 code (BP) slots and 0 literal slots
Info: Kinetis L-series (setup): Disabling watchdog.
Erasing device (MKL26Z128xxx4)...
Info: J-Link: Flash download: Flash programming performed for 1 range (1024 byte
s)
Info: J-Link: Flash download: Total time needed: 1.086s (Prepare: 0.465s, Compar
e: 0.143s, Erase: 0.017s, Program: 0.047s, Verify: 0.012s, Restore: 0.399s)
Erasing done.
J-Link>
To read further about MDM-AP Control register (check the output SWDReadAP), see chapter 9.3.1 MDM-AP Control Register where all bits are described.
Update1:
I am testing the KL46Z interface, got locked today, but was not able to revive it with the same procedure as above, unlocking failed firstly. I invoked erase, passed with a error, and the unlock. My chip is again alive!
SEGGER J-Link Commander V4.76f ('?' for help)
Compiled Sep 27 2013 16:54:08
DLL version V4.76f, compiled Sep 27 2013 16:53:51
Firmware: J-Link Lite-FSL V1 compiled Jun 25 2012 16:40:07
Hardware: V1.00
S/N: 361000149
VTarget = 3.280V
Info: Could not measure total IR len. TDO is constant high.
Info: Could not measure total IR len. TDO is constant high.
No devices found on JTAG chain. Trying to find device on SWD.
Info: Found SWD-DP with ID 0x0BC11477
****** Error: Error while identifying Cortex-M core.
Info: Found SWD-DP with ID 0x0BC11477
No device found on SWD.
Failed to identify target. Trying again with slow (4 kHz) speed.
Info: Could not measure total IR len. TDO is constant high.
Info: Could not measure total IR len. TDO is constant high.
No devices found on JTAG chain. Trying to find device on SWD.
Info: Found SWD-DP with ID 0x0BC11477
****** Error: Error while identifying Cortex-M core.
Info: Found SWD-DP with ID 0x0BC11477
No device found on SWD.
J-Link>device ?
Info: Device "MKL46Z256XXX4 (ALLOW SECURITY)" selected (256 KB flash, 32 KB RAM)
.
Reconnecting to target...
Info: Could not measure total IR len. TDO is constant high.
Info: Could not measure total IR len. TDO is constant high.
J-Link>unlock kinetis
Unlocking device...Timeout while unlocking device.
J-Link>unlock kinetis
Unlocking device...Timeout while unlocking device.
J-Link>unlock kinetis
Unlocking device...Timeout while unlocking device.
J-Link>erase
Info: Found SWD-DP with ID 0x0BC11477
****** Error: Kinetis (connect): Timeout while halting CPU. CPU does not stop.
Erasing device (MKL46Z256xxx4 (allow security))...
Info: Found SWD-DP with ID 0x0BC11477
Info: Found SWD-DP with ID 0x0BC11477
Info: Found Cortex-M0 r0p0, Little endian.
Info: FPUnit: 2 code (BP) slots and 0 literal slots
Info: Kinetis L-series (setup): Disabling watchdog.
Info: J-Link: Flash download: Flash programming performed for 1 range (1024 byte
s)
Info: J-Link: Flash download: Total time needed: 1.173s (Prepare: 0.481s, Compar
e: 0.245s, Erase: 0.016s, Program: 0.001s, Verify: 0.010s, Restore: 0.417s)
Erasing done.
J-Link>unlock kinetis
Unlocking device...O.K.
J-Link>