Electrical Characteristics
MPC8610 Integrated Host Processor Hardware Specifications, Rev. 2
Freescale Semiconductor
23
2.4.1
System Clock Timing
Table 9 provides the system clock (SYSCLK) AC timing specifications for the MPC8610.
2.4.1.1
SYSCLK and Spread Spectrum Sources
Spread spectrum clock sources are a popular way to control electromagnetic interference emissions (EMI) by spreading the
emitted noise over a wider spectrum and reducing the peak noise magnitude. These clock sources intentionally add long-term
jitter in order to diffuse the EMI spectral content. The jitter specification given in
Table 9 considers short-term (cycle-to-cycle)
jitter only and the clock generator’s cycle-to-cycle output jitter should meet the MPC8610 input cycle-to-cycle jitter
requirement. Frequency modulation and spread are separate concerns, and the MPC8610 is compatible with spread spectrum
sources if the recommendations listed in
Table 10 are observed.
It is imperative to note that the processor’s minimum and maximum SYSCLK, core, and VCO frequencies must not be exceeded
regardless of the type of clock source. Therefore, systems in which the processor is operated at its maximum rated e600 core
frequency should avoid violating the stated limits by using down-spreading only.
Table 9. SYSCLK AC Timing Specifications
Parameter/Condition
Symbol
Min
Typical
Max
Unit
Notes
SYSCLK frequency
fSYSCLK
33
—
133
MHz
1
SYSCLK cycle time
tSYSCLK
7.5
—
ns
—
SYSCLK rise and fall time
tKH, tKL
0.6
1.0
1.2
ns
2
SYSCLK duty cycle
tKHK/tSYSCLK
40
—
60
%
3
SYSCLK jitter
—
±150
ps
4, 5
Notes:
All specifications at recommended operating conditions (see Table 3) with OVDD = 3.3 V ± 165 mV. 1. Caution: The platform to SYSCLK clock ratio and e600 core to platform clock ratio settings must be chosen such that the
resulting SYSCLK, platform, and e600 (core) frequencies do not exceed their respective maximum or minimum operating
2. Rise and fall times for SYSCLK are measured at 0.4 and 2.7 V.
3. Timing is guaranteed by design and characterization.
4. This represents the short term jitter only and is guaranteed by design.
5. The SYSCLK driver’s closed loop jitter bandwidth should be <500 kHz at –20 dB. The bandwidth must be set low to allow
cascade-connected PLL-based devices to track SYSCLK drivers with the specified jitter. Note that the frequency modulation
for SYSCLK reduces significantly for the spread spectrum source case. This is to guarantee what is supported based on
design.
Table 10. Spread Spectrum Clock Source Recommendations
Parameter
Min
Max
Unit
Notes
Frequency modulation
—
50
kHz
1
Frequency spread
—
1.0
%
1, 2
Notes:
All specifications at recommended operating conditions (see
Table 3)
.
1. Guaranteed by design.
2. SYSCLK frequencies resulting from frequency spreading, and the resulting core and VCO frequencies, must meet the
minimum and maximum specifications given in
Table 10.