Xilinx virtex-5 fpga

228 www.xilinx.com Virtex-5 FPGA User Guide
UG190 (v5.0) June 19, 2009
Chapter 6: SelectIO Resources
Figure 6-13 illustrates a driver with single termination inside a Virtex-5 device.
Driver with Termination to V
CCO
/2 (Split Termination)
Some I/O standards, such as HSTL Class II, require an output termination to V
CCO
/2 (see
Figure 6-14).
DCI can provide output termination to V
CCO
/2 using split termination. DCI only controls
the impedance of the termination, but not the driver. Both HSTL and SSTL standards need
50 Ω external reference resistors. The DCI output standards supporting drivers with split
termination are shown in Table 6-2.
X-Ref Target - Figure 6-13
Figure 6-13: Driver with Termination to V
CCO
Using DCI Single Termination
R
UG190_6_11_021206
V
CCO
IOB
Z
0
Virtex-5 DCI
X-Ref Target - Figure 6-14
Figure 6-14: Driver with Termination to V
CCO
/2 without DCI
Table 6-2: DCI Output Standards Supporting Split Termination
HSTL_II_DCI DIFF_HSTL_II_DCI SSTL2_II_DCI DIFF_SSTL2_II_DCI
HSTL_II_DCI_18 DIFF_HSTL_II_DCI_18 SSTL18_II_DCI DIFF_SSTL18_II_DCI
R
UG190_c6_12_022609
V
CCO
/2
IOB
Z
0
Virtex-5 FPGA