System Bus Signal Quality Specifications
3.
System Bus Signal Quality Specifications
Source synchronous data transfer requires the clean reception of data signals and their associated
strobes. Ringing below receiver thresholds, non-monotonic signal edges, and excessive voltage
swing will adversely affect system timings. Ringback and signal non-monotinicity cannot be
tolerated since these phenomena may inadvertently advance receiver state machines. Excessive
signal swings (overshoot and undershoot) are detrimental to silicon gate oxide integrity and can
cause device failure if absolute voltage limits are exceeded. Additionally, overshoot and
undershoot can cause timing degradation due to the build up of inter-symbol interference (ISI)
effects. For these reasons, it is important that the designer work to achieve a solution that provides
acceptable signal quality across all systematic variations encountered in volume manufacturing.
This section documents signal quality metrics used to derive topology and routing guidelines
through simulation and for interpreting results for signal quality measurements of actual designs.
3.1
System Bus Clock (BCLK) Signal Quality Specifications
and Measurement Guidelines
Table 27 describes the signal quality specifications at the processor pads for the processor system
bus clock (BCLK) signals. Figure 25 describes the signal quality waveform for the system bus
clock at the processor pads.
Table 27. BCLK Signal Quality Specifications
Parameter
Min
Max
Unit
Figure
Notes1
BCLK[1:0] Overshoot
N/A
N/A
0.20
N/A
0.30
0.30
N/A
V
V
V
V
25
25
25
25
BCLK[1:0] Undershoot
BCLK[1:0] Ringback Margin
BCLK[1:0] Threshold Region
2
0.10
NOTES:
1. Unless otherwise noted, all specifications in this table apply to all Mobile Intel Pentium 4 Processor-M
frequencies.
2. The rising and falling edge ringback voltage specified is the minimum (rising) or maximum (falling) absolute
voltage the BCLK signal can dip back to after passing the VIH (rising) or VIL (falling) voltage limits. This
specification is an absolute value.
Mobile Intel Pentium 4 Processor-M Datasheet
51
INTEL [ INTEL ]
