Datasheet

The active background mode functions are managed through the background debug
controller (BDC) in the HCS08 V6 core. The BDC provides the means for analyzing
MCU operation during software development. Active background mode is entered in any
of the following ways:
• When the BKGD/MS pin is low at the time the MCU exits reset.
• When a BACKGROUND command is received through the BKGD pin.
• When a BGND instruction is executed.
• When encountering a BDC breakpoint.
Background commands are of two types:
• Non-intrusive commands, defined as commands that can be issued while the user
program is running. Non-intrusive commands can be issued through the BKGD pin
while the MCU is in run mode; non-intrusive commands can also be executed when
the MCU is in the active background mode. Non-intrusive commands include:
• Memory access commands
• Memory-access-with-status commands
• BDC register access commands
• The BACKGROUND command
• Active background commands, which can be executed only while the MCU is in
active background mode. Active background commands include commands to:
• Read or write CPU registers
• Trace one user program instruction at a time
• Leave active background mode to return to the user's application program (GO)
The active background mode is used to program a bootloader or user application program
into the flash program memory before the MCU is operated in run mode for the first time.
The active background mode can also be used to erase and reprogram the flash memory
after it has been previously programmed.
Chapter 10 Central processor unit
MC9S08PA60 Reference Manual, Rev. 1, 9/2012
Freescale Semiconductor, Inc. 263