Virtex-II Platform FPGAs: Functional Description
R
DS031-2 (v3.5) November 5, 2007
Module 2 of 4
Product Specification
6
Some input standards require a user-supplied threshold
voltage (VREF), and certain user-I/O pins are automatically
configured as VREF inputs. Approximately one in six of the
I/O pins in the bank assume this role.
VREF pins within a bank are interconnected internally, and
consequently only one VREF voltage can be used within
each bank. However, for correct operation, all VREF pins in
the bank must be connected to the external reference volt-
age source.
The VCCO and the VREF pins for each bank appear in the
device pinout tables. Within a given package, the number of
VREF and VCCO pins can vary depending on the size of
device. In larger devices, more I/O pins convert to VREF
pins. Since these are always a superset of the VREF pins
used for smaller devices, it is possible to design a PCB that
permits migration to a larger device if necessary.
All VREF pins for the largest device anticipated must be con-
nected to the VREF voltage and not used for I/O. In smaller
devices, some VCCO pins used in larger devices do not con-
nect within the package. These unconnected pins can be
left unconnected externally, or, if necessary, they can be
connected to VCCO to permit migration to a larger device.
Rules for Combining I/O Standards in the Same Bank
The following rules must be obeyed to combine different
input, output, and bi-directional standards in the same bank:
1.
Combining output standards only. Output standards
with the same output VCCO requirement can be
combined in the same bank.
Compatible example:
SSTL2_I and LVDS_25_DCI outputs
Incompatible example:
SSTL2_I (output VCCO = 2.5V) and
LVCMOS33 (output VCCO = 3.3V) outputs
2.
Combining input standards only. Input standards
with the same input VCCO and input VREF requirements
can be combined in the same bank.
Compatible example:
LVCMOS15 and HSTL_IV inputs
Incompatible example:
LVCMOS15 (input VCCO = 1.5V) and
LVCMOS18 (input VCCO = 1.8V) inputs
Incompatible example:
HSTL_I_DCI_18 (VREF = 0.9V) and
HSTL_IV_DCI_18 (VREF = 1.1V) inputs
3.
Combining input standards and output standards.
Input standards and output standards with the same
input VCCO and output VCCO requirement can be
combined in the same bank.
Compatible example:
LVDS_25 output and HSTL_I input
Incompatible example:
LVDS_25 output (output VCCO = 2.5V) and
HSTL_I_DCI_18 input (input VCCO = 1.8V)
4.
Combining bi-directional standards with input or
output standards. When combining bi-directional I/O
with other standards, make sure the bi-directional
standard can meet rules 1 through 3 above.
5.
Additional rules for combining DCI I/O standards.
a.
No more than one Single Termination type (input or
output) is allowed in the same bank.
Incompatible example:
HSTL_IV_DCI input and HSTL_III_DCI input
b.
No more than one Split Termination type (input or
output) is allowed in the same bank.
Incompatible example:
HSTL_I_DCI input and HSTL_II_DCI input
The implementation tools will enforce these design rules.
Table 5 summarizes all standards and voltage supplies.
Figure 7: Virtex-II I/O Banks: Top View for Wire-Bond
Packages (CS/CSG, FG/FGG, & BG/BGG)
Figure 8: Virtex-II I/O Banks: Top View for Flip-Chip
Packages (FF & BF)
ug002_c2_014_112900
Bank 0
Bank 1
Bank 5
Bank 4
Bank
7
Bank
6
Bank
2
Bank
3
ds031_66_112900
Bank 1
Bank 0
Bank 4
Bank 5
Bank
2
Bank
3
Bank
7
Bank
6