MC9S12T64 Datasheet, PDF (530/608 Pages) Motorola, Inc – Specification

Freescale Semiconductor, Inc.
Fast Background Debug Module (FBDM)
Secured Mode
If the user resets into special single chip mode with the part secured, a
secure BDM firmware lookup table is brought into the map along with the
standard BDM firmware lookup table. The secure BDM firmware is
higher priority than the standard BDM firmware. The secure BDM
firmware verifies that the FLASH is erased. This being the case, the
UNSEC bit is asserted (written to one). The BDM program jumps to start
of the standard BDM firmware and the secure BDM firmware is turned
off. If the FLASH do not verify as erased, the BDM firmware sets the
ENBDM bit, without asserting UNSEC, and the firmware enters a loop.
This causes the BDM hardware commands to become enabled, but
does not enable the software commands. This allows the BDM hardware
commands to be used to erase the FLASH.
Enabling and
Activating BDM
The system must be in active BDM to execute standard BDM firmware
commands. BDM can be activated only after being enabled. BDM is
enabled by setting the ENBDM bit in the BDM status (BDMSTS) register.
The ENBDM bit is set by writing to the BDM status (BDMSTS) register,
via the single-wire interface or via the BDM SPI interface, using a
hardware command such as WRITE_BD_BYTE.
After being enabled, BDM is activated by one of the following¹:
• Hardware BACKGROUND command
• BDM external instruction tagging mechanism
• CPU BGND instruction
• Breakpoint sub-block’s force or tag mechanism²
When BDM is activated, the CPU finishes executing the current
instruction and then begins executing the firmware in the standard BDM
firmware lookup table. When BDM is activated by the breakpoint
sub-block, the type of breakpoint used determines if BDM becomes
active before or after execution of the next instruction.
1. BDM is enabled and active immediately out of special single-chip reset (see Special Opera-
tion).
2. This method is only available on systems that have a a Breakpoint sub-block.
MC9S12T64Revision 1.1.1
Fast Background Debug Module (FBDM)
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