Chapter 5 Background Debug Controller (S12ZBDCV2)
S12ZVHY/S12ZVHL Family Reference Manual Rev. 1.05
150
Freescale Semiconductor
5.4
Functional Description
5.4.1
Security
If the device resets with the system secured, the device clears the BDCCSR UNSEC bit. In the secure state
BDC access is restricted to the BDCCSR register. A mass erase can be requested using the
ERASE_FLASH command. If the mass erase is completed successfully, the device programs the security
bits to the unsecure state and sets the BDC UNSEC bit. If the mass erase is unsuccessful, the device
remains secure and the UNSEC bit is not set.
For more information regarding security, please refer to device specific security information.
5.4.2
Enabling BDC And Entering Active BDM
BDM can be activated only after being enabled. BDC is enabled by setting the ENBDC bit in the BDCCSR
register, via the single-wire interface, using the command WRITE_BDCCSR.
After being enabled, BDM is activated by one of the following
1
:
•
The BDC BACKGROUND command
•
A CPU BGND instruction
•
The DBG Breakpoint mechanism
Alternatively BDM can be activated directly from reset when resetting into Special Single Chip Mode.
The BDC is ready for receiving the first command 10 core clock cycles after the deassertion of the internal
reset signal. This is delayed relative to the external pin reset as specified in the device reset documentation.
On S12Z devices an NVM initialization phase follows reset. During this phase the BDC commands
classified as always available are carried out immediately, whereas other BDC commands are subject to
delayed response due to the NVM initialization phase.
NOTE
After resetting into SSC mode, the initial PC address must be supplied by
the host using the WRITE_Rn command before issuing the GO command.
0
ILLCMD
Illegal Command Flag
— Indicates an illegal BDC command. This bit is set in the following cases:
When an unimplemented BDC command opcode is received.
When a DUMP_MEM{_WS}, FILL_MEM{_WS} or READ_SAME{_WS} is attempted in an illegal sequence.
When an active BDM command is received whilst BDM is not active
When a non Always-available command is received whilst the BDC is disabled or a flash mass erase is ongoing.
When a non Always-available command is received whilst the device is secure
Read commands return a value of 0xEE for each data byte
Writing a “1” to this bit, clears the bit.
0 No illegal command detected.
1 Illegal BDC command detected.
1. BDM active immediately out of special single-chip reset.
Table 5-6. BDCCSRL Field Descriptions (continued)
Field
Description
