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ColdFire Flash Module (CFM)
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
17-8
Freescale Semiconductor
17.3.3.2
CFMCLKD — CFM Clock Divider Register
The CFMCLKD register is used to control the period of the clock used for timed events in program and
erase algorithms.
All CFMCLKD register bits are readable, while bits [6:0] write once and bit 7 is not writable.
5
KEYACC
Enable security key writing
The KEYACC bit is readable and only writable if the KEYEN bits in the CFMSEC register are set to enable
backdoor key access.
1 = Writes to CFM flash memory are interpreted as keys to release security.
0 = Writes to CFM flash memory are interpreted as the start of a command write sequence.
4-0-
Reserved, reads as 0
IPSBAR
Offset:
0x1D_0002 (CFMCLKD)
Access: User read/write
7
6
5
4
3
2
1
0
R
DIVLD
PRDIV8
DIV
W
Reset:
0
0
0
0
0
0
0
0
Figure 17-5. CFM Clock Divider Register (CFMCLKD)
Table 17-5. CFMCLKD Field Descriptions
Field
Description
7
DIVLD
Clock divider loaded
1 = CFMCLKD register has been written to since the last reset.
0 = CFMCLKD register has not been written.
6
PRDIV8
Enable prescalar by 8
1 = Enables a prescalar to divide the internal flash bus clock by 8 before feeding into the clock divider.
0 = The internal flash bus clock is directly fed into the clock divider.
5-0
DIV
Clock divider bits
The combination of PRDIV8 and DIV effectively divides the internal flash bus clock down to a frequency
of 150 KHz - 200 KHz. The internal flash bus clock frequency range is 150 KHz < internal flash bus clock
< 102.4 MHz.
The CFMCLKD register bits PRDIV8 and DIV must be set with appropriate values before programming
or erasing the CFM flash memory
Section 17.4.2.3.1, “Writing the CFMCLKD Register
.”
Table 17-4. CFMMCR Field Descriptions (continued)
Field
Description
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