Clock Module
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor
7-7
14–12
MFD
Multiplication Factor Divider. Contain the binary value of the divider in the PLL feedback loop. The MFD[2:0]
value is the multiplication factor applied to the reference frequency. When MFD[2:0] are changed or the PLL
is disabled in stop mode, the PLL loses lock.
Note: In external clock mode, the MFD[2:0] bits have no effect.
11
LOCRE
Loss-of-clock reset enable. Determines how the system handles a loss-of-clock condition. When the
LOCEN bit is clear, LOCRE has no effect. If the LOCS flag in SYNSR indicates a loss-of-clock condition,
setting the LOCRE bit causes an immediate reset. To prevent an immediate reset, the LOCRE bit must be
cleared before entering stop mode with the PLL disabled.
0 No reset on loss-of-clock
1 Reset on loss-of-clock
Note: In external clock mode, the LOCRE bit has no effect.
10–8
RFD
Reduced frequency divider field. The binary value written to RFD[2:0] is the PLL frequency divisor; see
table in MFD bit description. Changes in clock frequency are synchronized to the next falling edge of the
current system clock.
Note: Changing RFD may cause a glitch in the PLL clock. To ensure correct operation of the PLL:
1. Bypass the PLL
2. Update RFD.
3. Select the PLL clock again.
The LPD (Low Power Divider) register can also be used to change system clock frequency.
7
LOCEN
Enables the loss-of-clock function. LOCEN does not affect the loss-of-lock function.
0 Loss-of-clock function disabled
1 Loss-of-clock function enabled
Note: In external clock mode, the LOCEN bit has no effect
.
6
DISCLK
Disable CLKOUT determines whether CLKOUT is driven. Setting the DISCLK bit holds CLKOUT low.
0 CLKOUT enabled
1 CLKOUT disabled
Table 7-4. SYNCR Field Descriptions (continued)
Field
Description
The following table shows the system frequency multiplier of the reference
frequency
1
in normal PLL mode.
1
f
sys
= f
ref
x 2(MFD + 2)/(2 exp RFD); f
ref
x 2(MFD + 2)
≤
60 MHz, f
sys
≤
MHz
MFD[2:0]
000
2
(4x)
2
MFD = 000 not valid for f
ref
< 3 MHz
001
(6x)
010
(8x)
(3)
011
(10x)
100
(12x)
101
(14x)
110
(16x)
111
(18x)
RF
D
[2
:0]
000 (
÷
1)
4
6
8
10
12
14
16
18
001 (
÷
2)
3
3
Default value out of reset
2
3
4
5
6
7
8
9
010 (
÷
4)
1
3/2
2
5/2
3
7/2
4
9/2
011 (
÷
8)
1/2
3/4
1
5/4
3/2
7/4
2
9/4
100 (
÷
16)
1/4
3/8
1/2
5/8
3/4
7/8
1
9/8
101 (
÷
32)
1/8
3/16
1/4
5/16
3/8
7/16
1/2
9/16
110 (
÷
64)
1/16
3/32
1/8
5/32
3/16
7/32
1/4
9/32
111 (
÷
128)
1/32
3/64
1/16
5/64
3/32
7/64
1/8
9/64
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:MCF52234CVM60,
MCF52235CVM60
