XC3S50 Datasheet, PDF (13/192 Pages) Xilinx, Inc – Revolutionary 90-nanometer process technology

Spartan-3 1.2V FPGA Family: Functional Description
R
match the characteristic impedance of the transmission line.
This adjustment process compensates for differences in I/O
impedance that can result from normal variation in the
ambient temperature, the supply voltage and the manufac-
turing process. When the output driver turns off, the series
termination, by definition, approaches a very high imped-
ance; in contrast, parallel termination resistors remain at the
targeted values.
DCI is available only for certain I/O standards, as listed in
Table 6. DCI is selected by applying the appropriate I/O
standard extensions to symbols or components. There are
five basic ways to configure terminations, as shown in
Table 7. The DCI I/O standard determines which of these
terminations is put into effect.
Table 6: DCI I/O Standards
Category of Signal
Standard
Signal Standard
V_CCO (V)
For
For
Outputs Inputs
V_REF for
Inputs (V)
Termination Type
At Output
At Input
Single-Ended
Gunning
Transceiver Logic
GTL_DCI
GTLP_DCI
1.2
1.2
0.8
1.5
1.5
1.0
Single
Single
High-Speed
HSTL_I_DCI
1.5
1.5
0.75
Transceiver Logic _{HSTL_III_DCI}
1.5
1.5
0.9
None
None
Split
Single
HSTL_I_DCI_18
1.8
1.8
0.9
None
Split
HSTL_II_DCI_18
1.8
1.8
0.9
Split
HSTL_III_DCI_18
1.8
1.8
1.1
None
Single
Low-Voltage CMOS LVDCI_15
LVDCI_18
1.5
1.5
1.8
1.8
-
Controlled impedance
None
-
driver
LVDCI_25
2.5
2.5
-
LVDCI_33
3.3
3.3
-
LVDCI_DV2_15
1.5
1.5
LVDCI_DV2_18
1.8
1.8
-
Controlled driver with
-
half-impedance
LVDCI_DV2_25
2.5
2.5
-
LVDCI_DV2_33
3.3
3.3
-
Stub Series
SSTL18_I_DCI
1.8
1.8
0.9
Terminated Logic
SSTL2_I_DCI
2.5
2.5
1.25
25-Ohm driver
Split
25-Ohm driver
SSTL2_II_DCI
2.5
2.5
1.25
Split with 25-Ohm driver
Differential
Low-Voltage
LVDS_25_DCI
2.5
2.5
-
Differential
Signalling
LVDSEXT_25_DCI 2.5
2.5
-
None
Split on
each line
of pair
Notes:
1. Bank 5 of any Spartan-3 device in a VQ100 or TQ144 package does not support DCI signal standards.
6
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DS099-2 (v1.2) July 11, 2003
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Advance Product Specification
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