mcf51ac256a Freescale Semiconductor, Inc, mcf51ac256a Datasheet - Page 37

• Manufacturer Part Number: mcf51ac256a
• Description: Mcf51ac Flexis
• Manufacturer: Freescale Semiconductor, Inc

Chapter 3
Modes of Operation
3.1
This chapter describes the operating modes of the MCF51AC256 series MCUs, and discusses entry, exit,
and device functionality pertaining to each mode.
The overall system mode is generally a function of a number of separate, but interrelated, variables: debug
mode, security mode, power mode and clock mode. Clock modes are discussed in
Modes of Operation.”
3.2
On this series of MCUs, wait, stop2, stop3 and stop4 are all entered via the CPU STOP instruction. See
Table 3-1
Freescale Semiconductor
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•
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Debug mode for code development — For devices based on the V1 ColdFire core, such as those
in the MCF51AC256 series, debug mode and secure mode are mutually exclusive.
Secure mode — BDC access to CPU resources is extremely restricted. It is possible to tell that the
device has been secured, and to clear security, which involves mass erasing the on-chip flash
memory. No other CPU access is allowed. Secure mode can be used in conjunction with each of
the power modes below.
Run mode — CPU clocks can be run at full speed, and the internal supply is fully regulated.
Wait mode — The CPU shuts down to conserve power; peripheral clocks are running and full
regulation is maintained.
Stop modes — System (CPU and bus) clocks are stopped.
— Stop4 — All internal circuits are powered (full regulation mode), LVD and/or BDM is enabled.
— Stop3 — All internal circuits are powered but in a standby state unless enabled in stop mode.
— Stop2 — Most internal circuits are powered-down. RAM content is retained but registers are
Introduction
Summary of Modes
and subsequent sections of this chapter for details.
Exited by RESET or active interrupt. Stop4 must be used to enable the ADC in stop mode.
LVD and BDM must be disabled. Exited by RESET or active interrupt. Stop3 is used to put the
MCU into its lowest power state while maintaining RAM and register contents.
powered-down. Exited by RESET, IRQ pin or RTI. Stop2 is the lowest power mode for this
device.
MCF51AC256 ColdFire Integrated Microcontroller Reference Manual, Rev. 5
This chapter covers the other dimensions of the system operating mode.
Section 16.4.1, “MCG
3-1