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MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor
4-7
4.4
Functional Description
4.4.1
Reset Vector Locations
The reset vector contains a pointer to the instruction where code execution begins after BAM execution.
The location of the reset vector is determined by boot mode, as illustrated in
.
4.4.2
Reset Sources
4.4.2.1
FMPLL Lock
A loss of lock of the FMPLL can cause a reset (provided the SIU is enabled by the
FMPLL_SYNCR[LOLRE] bit). Furthermore, reset will remain asserted, regardless of the source of reset,
until after the FMPLL has locked.
4.4.2.2
Flash High Voltage
There is no flash access gating signal implemented in the MPC5553/MPC5554. However, the device is
held in reset for a long enough period of time to guarantee that high voltage circuits are reset and stabilized
and that flash memory is accessible.
4.4.2.3
Reset Source Descriptions
For the following reset source descriptions refer to the reset flow diagrams in
shows the reset flow for assertion of the RESET pin.
shows the internal processing
of reset for all reset sources.
4.4.2.3.1
Power-on Reset
The power-on reset (POR) circuit is designed to detect a POR event and ensure that the RESET signal is
correctly sensed. The POR is not intended to be used to detect falling power supply voltages. External
supply monitoring should be provided. The output signals from the power-on reset circuits are active low
signals. All power-on reset output signals are combined into one POR signal at the V
DD
level and input to
the reset controller. Although assertion of the power-on reset signal causes reset, the RESET pin must be
asserted during a power-on reset to guarantee proper operation of the MCU.
Table 4-4. Reset Vector Locations
Boot Mode
Reset Vector Location
External Boot
0x0000_0004 (assuming 0x0000_0000 has a valid RCHW)
Internal Boot
Next word address after the first valid RCHW found. The BAM searches the lowest
address of each of the six low address space blocks in flash memory for a valid
RCHW. Hence, the possible reset vector locations are:
0x0000_0004
0x0000_4004
0x0001_0004
0x0001_C004
0x0002_0004
0x0003_0004
Serial Boot
Specified over serial download
Содержание MPC5553
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