MC9S12HY64 Datasheet, PDF (164/792 Pages) Freescale Semiconductor, Inc – S12 Microcontrollers

Background Debug Module (S12SBDMV1)
5.3.2.1 BDM Status Register (BDMSTS)
Register Global Address 0x3_FF01
7
R
ENBDM
W
Reset
Special Single-Chip Mode
0¹
All Other Modes
0
6
5
BDMACT
0
4
SDV
1
0
0
0
0
0
= Unimplemented, Reserved
3
2
1
0
TRACE
0
UNSEC
0
0
0
0²
0
0
0
0
0
= Implemented (do not alter)
0
= Always read zero
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). This is because the ENBDM bit is set by the standard firmware before a BDM command can be fully
transmitted and executed.
2 _{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).
Figure 5-3. 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 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
7
ENBDM
6
BDMACT
Description
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.
0 BDM disabled
1 BDM enabled
Note: ENBDM is set by the firmware out of reset in special single chip mode. In special single chip mode with
the device secured, this bit will not be set by the firmware until after the Flash erase verify tests are
complete.
BDM Active Status — This bit becomes set upon entering BDM. The standard BDM firmware lookup table is
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
MC9S12HY/HA-Family Reference Manual, Rev. 1.04
164
Freescale Semiconductor