Intel III Xeon 800 MHz 80526KZ800256 User Manual
Product codes
80526KZ800256
SIGNAL QUALITY
39
1.
Activity Factor based on period equal to 30 nS.
2.
Overshoot/Undershoot Magnitude = 2.3V is an Absolute value and should never be exceeded.
3.
Overshoot is measured relative to VSS.
4.
Undershoot is measured relative to VTT.
5.
Overshoot/Undershoot Pulse Duration is measured relative to 1.635V.
6.
Ringback below VTT cannot be subtracted from Overshoots/Undershoots.
7.
Lesser Undershoot does not allocate longer or larger Overshoot.
8.
OEM's are encouraged to follow Intel provided layout guidelines.
9.
All values specified by design characterization.
4.3.2 BCLK Overshoot/Undershoot Guidelines and Specifications
Unlike AGTL+ or CMOS signals, BCLK Specifications do not provide for any relaxation due to activity factor. System
designers should ensure that their platforms meet the BCLK specifications even under worst-case conditions.
Intel recommends that platforms meet the Absolute Maximum Specifications for Overshoot and Undershoot on BCLK.
This ensures that the BCLK I/O buffer will meet specifications regardless of Overshoot or Undershoot Pulse Duration
within a clock cycle with 50% duty cycle. For all processors, the maximum BCLK Overshoot level is 3.3V. The Absolute
maximum Undershoot is –0.7V, where “maximum” is defined as the largest voltage potential below ground.
However, the Absolute Maximum Specifications can be relaxed for BCLK Undershoot if the Pulse Duration is accounted
for under worst-case conditions. Thus, a system with BCLK Undershoot below -0.7V must ensure that the worst case
Pulse Duration is less than or equal to the allowed Max Pulse Duration for the Worst Case Undershoot Magnitude. See
the tables in this section for complete details.
designers should ensure that their platforms meet the BCLK specifications even under worst-case conditions.
Intel recommends that platforms meet the Absolute Maximum Specifications for Overshoot and Undershoot on BCLK.
This ensures that the BCLK I/O buffer will meet specifications regardless of Overshoot or Undershoot Pulse Duration
within a clock cycle with 50% duty cycle. For all processors, the maximum BCLK Overshoot level is 3.3V. The Absolute
maximum Undershoot is –0.7V, where “maximum” is defined as the largest voltage potential below ground.
However, the Absolute Maximum Specifications can be relaxed for BCLK Undershoot if the Pulse Duration is accounted
for under worst-case conditions. Thus, a system with BCLK Undershoot below -0.7V must ensure that the worst case
Pulse Duration is less than or equal to the allowed Max Pulse Duration for the Worst Case Undershoot Magnitude. See
the tables in this section for complete details.
Table 28. BCLK Undershoot Specifications
1,2,3,4,5,6
Undershoot
Max Pulse Duration (nS)
Magnitude
-0.85 2.13
-0.8 2.80
-0.75 3.73
-0.7 5.00
-0.65 5.00
NOTES:
1.
Undershoot is measured relative to VTT.
2.
Overshoot/Undershoot Pulse Duration is measured relative to 1.635V.
3.
Ringback below VTT cannot be subtracted from Overshoots/Undershoots.
4.
Lesser Undershoot does not allocate longer or larger Overshoot.
5.
OEM's are encouraged to follow Intel provided layout guidelines.
6.
All values specified by design characterization.
4.3.3 Measuring BCLK Overshoot/Undershoot
Overshoot on BCLK is measured relative to GND. By probing BCLK with an oscilloscope where the probe GND lead
makes good contact to a processor GND pin, BCLK Overshoot can be accurately measured to determine if the system
meets BCLK Overshoot Absolute Maximum Specifications.
Undershoot on BCLK is also measured relative to GND, again by probing BCLK with an oscilloscope where the probe
GND lead makes good contact to a processor GND pin. If the system does not meet the BCLK Undershoot Absolute
Maximum Specifications, then the Worst Case Undershoot Magnitude must be measured and the Pulse Duration of the
Undershoot must be accounted for. Pulse Duration measurements determine the total amount of time that the BCLK
signal spends below GND. Measuring from the earliest Falling Edge GND crossover to the latest Rising Edge GND
crossover provides the worst-case Undershoot Pulse Duration. When compared to the Specification Table, the Pulse
Duration and the Worst Case Undershoot Magnitude then determines if the system meets the BCLK
Overshoot/Undershoot Specifications. Note: the measured Pulse Duration must be less than or equal to the Specified
Max Pulse Duration for a given Worst Case Undershoot Magnitude.
makes good contact to a processor GND pin, BCLK Overshoot can be accurately measured to determine if the system
meets BCLK Overshoot Absolute Maximum Specifications.
Undershoot on BCLK is also measured relative to GND, again by probing BCLK with an oscilloscope where the probe
GND lead makes good contact to a processor GND pin. If the system does not meet the BCLK Undershoot Absolute
Maximum Specifications, then the Worst Case Undershoot Magnitude must be measured and the Pulse Duration of the
Undershoot must be accounted for. Pulse Duration measurements determine the total amount of time that the BCLK
signal spends below GND. Measuring from the earliest Falling Edge GND crossover to the latest Rising Edge GND
crossover provides the worst-case Undershoot Pulse Duration. When compared to the Specification Table, the Pulse
Duration and the Worst Case Undershoot Magnitude then determines if the system meets the BCLK
Overshoot/Undershoot Specifications. Note: the measured Pulse Duration must be less than or equal to the Specified
Max Pulse Duration for a given Worst Case Undershoot Magnitude.