Appendix A Electrical Characteristics
MC9S12XDP512 Data Sheet, Rev. 2.11
Freescale Semiconductor 949
The relative deviation of t
nom
is at its maximum for one clock period, and decreases towards zero for larger
number of clock periods (N).
Defining the jitter as:
For N < 1000, the following equation is a good fit for the maximum jitter:
Figure A-5. Maximum Bus Clock Jitter Approximation
This is very important to notice with respect to timers, serial modules where a prescaler will eliminate the
effect of the jitter to a large extent.
JN() max 1
t
max
N()
Nt
nom
⋅
-----------------------
– 1
t
min
N()
Nt
nom
⋅
-----------------------
–,
⎝⎠
⎜⎟
⎛⎞
=
JN()
j
1
N
--------
j
2
+=
1 5 10 20 N
J(N)