SLAU320AJ July 2010 – May 2021
The FR4xx and FR2xx device families do not support JTAG protection by a user-defined password. These device families have only a simple JTAG lock mechanism. If a JTAG lock signature is written to memory address 0xFF80, JTAG access is locked. To unlock these device families, a special erase command (User_Code_Erase 0x1A1A) must be applied through the JTAG mailbox (see the following detailed sequence diagram).
Restart device, initialize JTAG and feed in Erase command while device is in reset | |
ClrTST() | Restart device |
ClrRST() | Restart device |
StartJtag(RSTLOW) | Restart JTAG – Keep RST low device do not start |
ResetTAP() | Reset JTAG TAP state machine |
IR_Shift(IR_JMB_EXCHANGE) | Do JTAG mailbox exchange request |
DR_Shift(0xA55A) | Send device after BootCode execution into LPM4 |
DR_Shift(0x1A1A) | Send device UserCode erase command |
Stop JTAG (release device to run) | |
Wait until BootCode is executed and device is in LPM4 | |
Initialize JTAG access (Rest Tap) | |
Get back JTAG control calling SyncJtag_AssertPor() function |