Background Debug Module (S12SBDMV1)
Read: All modes through BDM operation when not secured
Write: All modes through BDM operation when not secured, but subject to the following:
— ENBDM should only be set via a BDM hardware command if the BDM firmware commands
are needed. (This does not apply in special single chip mode).
— BDMACT can only be set by BDM hardware upon entry into BDM. It can only be cleared by
the standard BDM firmware lookup table upon exit from BDM active mode.
— All other bits, while writable via BDM hardware or standard BDM firmware write commands,
should only be altered by the BDM hardware or standard firmware lookup table as part of BDM
command execution.
Table 5-2. BDMSTS Field Descriptions
Field
Description
7
Enable BDM — This bit controls whether the BDM is enabled or disabled. When enabled, BDM can be made
active to allow firmware commands to be executed. When disabled, BDM cannot be made active but BDM
hardware commands are still allowed.
ENBDM
0 BDM disabled
1 BDM enabled
Note: ENBDM is set out of reset in special single chip mode. In special single chip mode with the device
secured, this bit will not be set until after the Flash erase verify tests are complete.
6
BDM Active Status — This bit becomes set upon entering BDM. The standard BDM firmware lookup table is
BDMACT
then enabled and put into the memory map. BDMACT is cleared by a carefully timed store instruction in the
standard BDM firmware as part of the exit sequence to return to user code and remove the BDM memory from
the map.
0 BDM not active
1 BDM active
4
SDV
Shift Data Valid — This bit is set and cleared by the BDM hardware. It is set after data has been transmitted as
part of a BDM firmware or hardware read command or after data has been received as part of a BDM firmware
or hardware write command. It is cleared when the next BDM command has been received or BDM is exited.
SDV is used by the standard BDM firmware to control program flow execution.
0 Data phase of command not complete
1 Data phase of command is complete
3
TRACE1 BDM Firmware Command is Being Executed — This bit gets set when a BDM TRACE1 firmware
command is first recognized. It will stay set until BDM firmware is exited by one of the following BDM commands:
GO or GO_UNTIL.
TRACE
0 TRACE1 command is not being executed
1 TRACE1 command is being executed
1
Unsecure — If the device is secured this bit is only writable in special single chip mode from the BDM secure
firmware. It is in a zero state as secure mode is entered so that the secure BDM firmware lookup table is enabled
and put into the memory map overlapping the standard BDM firmware lookup table.
UNSEC
The secure BDM firmware lookup table verifies that the on-chip Flash is erased. This being the case, the UNSEC
bit is set and the BDM program jumps to the start of the standard BDM firmware lookup table and the secure
BDM firmware lookup table is turned off. If the erase test fails, the UNSEC bit will not be asserted.
0 System is in a secured mode.
1 System is in a unsecured mode.
Note: When UNSEC is set, security is off and the user can change the state of the secure bits in the on-chip
Flash EEPROM. Note that if the user does not change the state of the bits to “unsecured” mode, the
system will be secured again when it is next taken out of reset.After reset this bit has no meaning or effect
when the security byte in the Flash EEPROM is configured for unsecure mode.
S12P-Family Reference Manual, Rev. 1.13
136
Freescale Semiconductor
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