MC9RS08KA1 FREESCALE [Freescale Semiconductor, Inc], MC9RS08KA1 Datasheet - Page 22

• Manufacturer Part Number: MC9RS08KA1
• Description: RS08 Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Chapter 3 Modes of Operation
After active background mode is entered, the CPU is held in a suspended state waiting for serial
background commands rather than executing instructions from the user application program.
Background commands are of two types:
Active background mode is used to program user application code into the Flash program memory before
the MCU is operated in run mode for the first time. When the MC9RS08KA2 Series is shipped from the
Freescale Semiconductor factory, the Flash program memory is usually erased so there is no program that
could be executed in run mode until the Flash memory is initially programmed. The active background
mode can also be used to erase and reprogram the Flash memory after it has been previously programmed.
For additional information about the active background mode, refer to the
of this data sheet.
3.5
Wait mode is entered by executing a WAIT instruction. Upon execution of the WAIT instruction, the CPU
enters a low-power state in which it is not clocked. The program counter (PC) is halted at the position
where the WAIT instruction is executed. When an interrupt request occurs:
It is the responsibility of the user program to probe the corresponding interrupt source that woke the MCU,
because no vector fetching process is involved.
While the MCU is in wait mode, not all background debug commands can be used. Only the
BACKGROUND command and memory-access-with-status commands are available when the MCU is in
wait mode. The memory-access-with-status commands do not allow memory access, but they report an
error indicating that the MCU is in either stop or wait mode. The BACKGROUND command can be used
to wake the MCU from wait mode and enter active background mode.
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1. MCU exits wait mode and resumes processing.
2. PC is incremented by one and fetches the next instruction to be processed.
When a BDC breakpoint is encountered
Non-intrusive commands, defined as commands that can be issued while the user program is
running, 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
— BACKGROUND command
Active background commands, which can be executed only while the MCU is in active background
mode, 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 application program (GO)
Wait Mode
MC9RS08KA2 Series Data Sheet, Rev. 3
Development Support
Freescale Semiconductor
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