Clock Module
MCF52277 Reference Manual, Rev. 1
7-8
Freescale Semiconductor
7.2.2
PLL Status Register (PSR)
The PSR register enables loss-of-lock reset and interrupt, and also indicates the PLL lock status.
7.3
Functional Description
This subsection provides a functional description of the clock module.
7.3.1
PLL Frequency Multiplication Factor Select
The frequency multiplication factor of the PLL is defined by the feedback divider and output dividers. An
example equation for the core frequency is given below:
Eqn. 7-6
where
f
sys
is the clock frequency of the ColdFire core and
f
REF
is the PLL clock source as shown in
. The allowable range of values for the PFDR is 4 to 34 and OUTDIV
n
is 1 to 15. However,
PFDR must also be selected such that the VCO frequency (
f
REF
×
PCR[PFDR]) is of the range
300–540 MHz. The other clocks on the processor are configurable in a similar fashion. However, there are
various dependencies. See
Section 7.2.1, “PLL Control Register (PCR),”
for details.
Address: 0xFC0C_0004 (PSR)
Access: User read/write
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
LOL
RE
LOL
IRQ
LOCK LOCKS
W
Reset 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0
0
0
0
Figure 7-4. PLL Status Register (PSR)
Table 7-4. PSR Field Descriptions
Field
Description
31–4
Reserved, must be cleared.
3
LOLRE
PLL loss of lock reset enable. Because reset clears the PSR register, if this bit is set and a loss-of-lock occurs, the
user must read the reset status register (RSR) to determine a loss-of-lock condition occurred. See
for more details on RSR.
0 Loss of lock does not generate a reset.
1 Loss of lock generates a reset to the device.
2
LOLIRQ
PLL loss-of-lock interrupt enable. Enables an interrupt request to generate when the PLL loses lock.
0 Loss-of-lock does not generate an interrupt request.
1 Loss-of-lock generates an interrupt request.
1
LOCK
PLL lock status. Indicates a locked PLL. See
Section 7.3.2, “Lock Conditions,”
for more details.
0 PLL is not locked.
1 PLL is locked.
0
LOCKS
PLL lost lock. Indicates that the PLL has lost lock. If the PFDR field changes or if an unexpected loss-of-lock condition
occurs, this bit is set. This bit is sticky and the user must clear it before the PLL can write the register again.
0 PLL has not lost lock.
1 PLL has lost lock.
f
SYS
f
REF
PCR PFDR
[
]
PCR OUTDIV1
[
]
1
+
------------------------------------------------------
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Summary of Contents for MCF52277
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