Datasheet

1-12 MCF5307 User’s Manual
Programming Model, Addressing Modes, and Instruction Set
Figure 1-3. PLL Module
The PLL module’s three modes of operation are described as follows.
• Reset mode—When RSTI
is asserted, the PLL enters reset mode. At reset, the PLL
asserts RST
O from the MCF5307. The core:bus frequency ratio and other MCF5307
configuration information are sampled during reset.
• Normal mode—In normal mode, the input frequency programmed at reset is
clock-multiplied to provide the processor clock (PCLK).
• Reduced-power mode—In reduced-power mode, the PCLK is disabled by executing
a sequence that includes programming a control bit in the system configuration
register (SCR) and then executing the STOP instruction. Register contents are
retained in reduced-power mode, so the system can be reenabled quickly when an
unmasked interrupt or reset is detected.
1.4 Programming Model, Addressing Modes, and
Instruction Set
The ColdFire programming model has two privilege levels—supervisor and user. The S bit
in the status register (SR) indicates the privilege level. The processor identifies a logical
address that differentiates between supervisor and user modes by accessing either the
supervisor or user address space.
• User mode—When the processor is in user mode (SR[S] = 0), only a subset of
registers can be accessed, and privileged instructions cannot be executed. Typically,
most application processing occurs in user mode. User mode is usually entered by
executing a return from exception instruction (RTE, assuming the value of SR[S]
saved on the stack is 0) or a MOVE, SR instruction (assuming SR[S] is 0).
• Supervisor mode—This mode protects system resources from uncontrolled access
by users. In supervisor mode, complete access is provided to all registers and the
entire ColdFire instruction set. Typically, system programmers use the supervisor
programming model to implement operating system functions and provide I/O
PLL
CLKIN
RSTI
Divide
BCLKO
DIVIDE[1:0]
FREQ[1:0]
RSTO
PSTCLK
PCLK
CLKIN X 4 by 2
Divide by 2,
3, or 4
Fr
eescale S
emiconduct
or
, I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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