Chapter 15 Background Debug Module (S12XBDMV2)
MC9S12XDP512 Data Sheet, Rev. 2.17
574
Freescale Semiconductor
15.3.2.1
BDM Status Register (BDMSTS)
Figure 15-3. BDM Status Register (BDMSTS)
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 rmware commands
are needed. (This does not apply in special single chip and emulation modes).
— BDMACT can only be set by BDM hardware upon entry into BDM. It can only be cleared by
the standard BDM rmware lookup table upon exit from BDM active mode.
— CLKSW can only be written via BDM hardware WRITE_BD commands.
— All other bits, while writable via BDM hardware or standard BDM rmware write commands,
should only be altered by the BDM hardware or standard rmware lookup table as part of BDM
command execution.
Register Global Address 0x7FFF01
7
6
54
3
2
1
0
R
ENBDM
BDMACT
0SDV
TRACE
CLKSW
UNSEC
0
W
Reset
Special Single-Chip Mode
01
1 ENBDM is read as 1 by a debugging environment in special single chip mode when the device is not secured or secured but
fully erased (Flash and EEPROM). This is because the ENBDM bit is set by the standard rmware before a BDM command
can be fully transmitted and executed.
1
00
0
03
3 UNSEC is read as 1 by a debugging environment in special single chip mode when the device is secured and fully erased,
else it is 0 and can only be read if not secure (see also bit description).
0
Emulation Modes
1
0
00
0
12
2 CLKSW is read as 1 by a debugging environment in emulation modes when the device is not secured and read as 0 when
secured.
0
All Other Modes
0
00
0
= Unimplemented, Reserved
= Implemented (do not alter)
0
= Always read zero
Table 15-2. BDMSTS Field Descriptions
Field
Description
7
ENBDM
Enable BDM — This bit controls whether the BDM is enabled or disabled. When enabled, BDM can be made
active to allow rmware commands to be executed. When disabled, BDM cannot be made active but BDM
hardware commands are still allowed.
0 BDM disabled
1 BDM enabled
Note: ENBDM is set by the rmware out of reset in special single chip mode and by hardware in emulation
modes. In special single chip mode with the device secured, this bit will not be set by the rmware until
after the EEPROM and Flash erase verify tests are complete. In emulation modes with the device
secured, the BDM operations are blocked.