S912XEG384J3VA Datasheet, PDF (280/1324 Pages) Freescale Semiconductor, Inc – MC9S12XEP100 Reference Manual Covers MC9S12XE Family

Chapter 7 Background Debug Module (S12XBDMV2)
• Hardware handshake protocol to increase the performance of the serial communication
• Active out of reset in special single chip mode
• Nine hardware commands using free cycles, if available, for minimal CPU intervention
• Hardware commands not requiring active BDM
• 14 firmware commands execute from the standard BDM firmware lookup table
• Software control of BDM operation during wait mode
• Software selectable clocks
• Global page access functionality
• Enabled but not active out of reset in emulation modes (if modes available)
• CLKSW bit set out of reset in emulation modes (if modes available).
• When secured, hardware commands are allowed to access the register space in special single chip
mode, if the non-volatile memory erase test fail.
• Family ID readable from firmware ROM at global address 0x7FFF0F (value for HCS12X devices
is 0xC1)
• BDM hardware commands are operational until system stop mode is entered (all bus masters are
in stop mode)
7.1.2 Modes of Operation
BDM is available in all operating modes but must be enabled before firmware commands are executed.
Some systems may have a control bit that allows suspending thefunction during background debug mode.
7.1.2.1 Regular Run Modes
All of these operations refer to the part in run mode and not being secured. The BDM does not provide
controls to conserve power during run mode.
• Normal modes
General operation of the BDM is available and operates the same in all normal modes.
• Special single chip mode
In special single chip mode, background operation is enabled and active out of reset. This allows
programming a system with blank memory.
• Emulation modes (if modes available)
In emulation mode, background operation is enabled but not active out of reset. This allows
debugging and programming a system in this mode more easily.
7.1.2.2 Secure Mode Operation
If the device is in secure mode, the operation of the BDM is reduced to a small subset of its regular run
mode operation. Secure operation prevents BDM and CPU accesses to non-volatile memory (Flash and/or
EEPROM) other than allowing erasure. For more information please see Section 7.4.1, “Security”.
MC9S12XE-Family Reference Manual Rev. 1.25
280
Freescale Semiconductor