MPC555
/
MPC556
CDR MoneT FLASH EEPROM
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
19-29
19.7.4 Exponential Clock Multiplier
The second term in the pulse width timing equation is the exponential clock multiplier,
N. The program pulse number (pulse), clock period exponent (CLKPE), CSC, and PE
define the exponent in the 2
N
multiply of the clock period. The exponent, N, is defined
by the equation:
N = 5 + CLKPE[0:1] + ((PE | CSC)
•
10)
All of the exponents are shown in
19.7.5 Linear Clock Multiplier
The third term of the pulse width timing equation is the linear clock multiplier, M. The
clock period multiplier, CLKPM[0:6], defines a linear multiplier for the program or erase
pulse. The multiplier, M, is defined by the equation:
M = 1 + CLKPM[0:6]
This allows for the program/erase pulse to be from one to 128 times the pulse set by
the system clock period, SCLKR[0:2] and CLKPE[0:1].
The default reset state of CLKPM[0:6] = 000 0000 for a multiplier of one.
19.7.6 A Technique to Determine SCLKR, CLKPE, and CLKPM
The following example determines the values of the SCLKR, CLKPE, and CLKPM
fields for a 25.6
µ
s program pulse, PE = 0, in a system with a 40 MHz system clock.
Table 19-13 Clock Period Exponent and Pulse Width Range
PE |
CSC
CLKPE[0:1]
Exponent
(N)
Pulse Width Range for all System Clock
Frequencies from 8.0 MHz to 40.0 MHz.
Minimum Pulse Width
Maximum Pulse Width
8 MHz
1
2
N
•1.25E-7
NOTES:
1. CMF clock frequency after SCKLR scaling. Example: A 40 MHz system clock scaled by 4 (SCLKR[0:2] = 0b101)
results in an equivalent CMF clock of 10 MHz.
10 MHz
1
2
N
•1E-7
12 MHz
1
2
N
•0.833E-7
8 MHz
1
2
N
•1.25E-07
10 MHz
1
2
N
•1E-7
12 MHz
1
2
N
•0.833E-7
0
00
5
4 µs
3.2 µs
2.7 µs
512 µs
409.6 µs
341.3 µs
01
6
8 µs
6.4 µs
5.3 µs
1.024 ms
819.2 µs
682.7 µs
10
7
16 µs
12.8 µs
10.7 µs
2.048 ms
1.6384 ms
1.365 ms
11
8
32 µs
25.6 µs
21.3 µs
4.096 ms
3.2768 ms
2.731 ms
1
00
15
4.096 ms
3.28 ms
2.73 ms
524.29 ms
419.43 ms
349.5 ms
01
16
8.192 ms
6.55 ms
5.46 ms
1.05 s
838.86 ms
699.1 ms
10
17
16.384 ms
13.11 ms
10.92 ms
2.10 s
1.68 s
1.398 s
11
18
32.768 ms 26.21 ms
21.85 ms
4.19 s
3.35 s
2.796 s
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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