MC9S12Q128_10 Datasheet, PDF (620/644 Pages) Freescale Semiconductor, Inc – HCS12 Microcontrollers

Appendix A Electrical Characteristics
0
1
2
3
N-1
N
t_min1
t_nom
t_max1
t_minN
t_maxN
Figure A-3. Jitter Definitions
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:
J(N)
=
⎛
max_⎜
⎝
1 – -tN-^m-----_â‹^a---t^x-_n--⁽--_o-N--_m--⁾- ,
1
–
N-t--^m---⋅^-i--nt--_n^-(--_o^-N---_m^-)-
⎞
⎟
⎠
For N < 100, the following equation is a good fit for the maximum jitter:
J(N)
=
---^j--¹---
N
+
j₂
J(N)
1
5
10
20
N
Figure A-4. Maximum Bus Clock Jitter Approximation
This is very important to notice with respect to timers, serial modules where a pre-scaler will eliminate the
effect of the jitter to a large extent.
620
MC9S12Q128
Freescale Semiconductor
Rev 1.10