Spartan-3A/3AN FPGA Starter Kit Board User Guide
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127
UG334 (v1.1) June 19, 2008
Differential I/O Connectors
R
inputs, the differential input is converted to a single-ended clock signal within the
FPGA. This clock input then feeds the upper-right DCM, labeled as DCM_X2Y3.
Figure 15-6:
Differential I/O Layout
FPGA
“Receive” Header (J2)
“Transmit” Header (J15)
1
2
33
34
1
2
33
34
All traces routed with 100
Ω
matched impedance.
All “receive” pairs routed with matched trace lengths
within 0.25 inches.
Receive clock pair connects to global clock inputs
GCLK7 and GCLK8 that feed the top-right DCM
labeled DCM_X2Y3.
All traces routed with 100
Ω
matched impedance.
All “transmit” pairs routed with matched trace lengths
within 0.25 inches.
Bank 0
Bank 2
If using for differential inputs, set the DIFF_TERM=TRUE constraint.
There are no external termination resistors provided on the board.
UG330_c12_15_012407