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www.xilinx.com
ML365 Virtex-II Pro QDR II SRAM Mem. Board
1-800-255-7778
UG066 (v1.0) June 29, 2004
Chapter 4:
Signal Integrity Recommendations and Simulations
R
Terminations and Transmission Lines for QDR Components
Data and Clock Signals (D, Q, CQ, CQ, and CLK)
For the QDR signals included in the data bus D, the terminations consist of a 50 ohm
parallel termination pulled-up to 0.9 Volts. As DCI is used in the FPGA, no termination is
required.
Use 50 ohm transmission lines with less than ±1% tolerance on the transmission line
impedance. The recommendations for the transmission line lengths are:
•
All the data and clock signals are point-to-point from the FPGA to each QDR
component. The flight time of the signals going to one individual QDR II SRAM
component need to be matched with respect to the other signals with a ±2% tolerance.
•
All signals going to the memory component have been matched within a 200 ps.
window. This timing requirement includes the FPGA internal package skew
(available in
) and the skew between the ball of the FPGA
to the resistor pack as well as the length of the actual trace.
•
The IBIS simulation provided in
have been processed
using the actual PCB characteristics, from the PCB layout tool and the memory and
FPGA driver IBIS models.
Address and Control Signals (A, R, W, BW)
For the address and control signals, no termination is required at the FPGA. At memory, a
50 ohm resistor pulled up to 0.9 V is used to terminate the transmission line.
Use 50 ohm transmission lines with ± 5% tolerance from the FPGA to all the memory
components. The recommendations for the transmission line lengths are as follows:
•
All the data and clock signals are point-to-point from the FPGA to each QDR
component. The flight time of the signals going to one individual QDR II SRAM
component need to be matched with respect to to the other signals with a ± 2%
tolerance.
•
All signals going to the memory component have been matched within a 200 ps.
window. This timing requirement includes the FPGA internal package skew
(available in
) and the skew between the ball of the FPGA
to the resistor pack as well as the length of the actual trace.
•
The IBIS simulation provided in
have been processed
using the actual PCB characteristics, from the PCB layout tool and the memory and
FPGA driver IBIS models.
Product Not Recommended for New Designs