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Virtex-II Platform FPGAs: Detailed Description
R
DS031-2 (v3.0) August 1, 2003
Product Specification
1-800-255-7778Module 2 of 4
6
Eight I/O banks result from dividing each edge of the FPGA
into two banks, as shown in
Figure 7
and
Figure 8
. Each
bank has multiple V
CCO
pins, all of which must be con-
nected to the same voltage. This voltage is determined by
the output standards in use.
Some input standards require a user-supplied threshold
voltage (V
REF
), and certain user-I/O pins are automatically
configured as V
REF
inputs. Approximately one in six of the
I/O pins in the bank assume this role.
V
REF
pins within a bank are interconnected internally, and
consequently only one V
REF
voltage can be used within
each bank. However, for correct operation, all V
REF
pins in
the bank must be connected to the external reference volt-
age source.
The V
CCO
and the V
REF
pins for each bank appear in the
device pinout tables. Within a given package, the number of
V
REF
and V
CCO
pins can vary depending on the size of
device. In larger devices, more I/O pins convert to V
REF
pins. Since these are always a superset of the V
REF
pins
used for smaller devices, it is possible to design a PCB that
permits migration to a larger device if necessary.
All V
REF
pins for the largest device anticipated must be con-
nected to the V
REF
voltage and not used for I/O. In smaller
devices, some V
CCO
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 V
CCO
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 V
CCO
requirement can be
combined in the same bank.
Compatible example:
SSTL2_I and LVDS_25_DCI outputs
Incompatible example:
SSTL2_I (output V
CCO
= 2.5V) and
LVCMOS33 (output V
CCO
= 3.3V) outputs
2.
Combining input standards only.
Input standards
with the same input V
CCO
and input V
REF
requirements
can be combined in the same bank.
Compatible example:
LVCMOS15 and HSTL_IV inputs
Incompatible example:
LVCMOS15 (input V
CCO
= 1.5V) and
LVCMOS18 (input V
CCO
= 1.8V) inputs
Incompatible example:
HSTL_I_DCI_18 (V
REF
= 0.9V) and
HSTL_IV_DCI_18 (V
REF
= 1.1V) inputs
3.
Combining input standards and output standards.
Input standards and output standards with the same
input V
CCO
and output V
CCO
requirement can be
combined in the same bank.
Compatible example:
LVDS_25 output and HSTL_I input
Incompatible example:
LVDS_25 output (output V
CCO
= 2.5V) and
HSTL_I_DCI_18 input (input V
CCO
= 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.
Figure 7:
Virtex-II I/O Banks: Top View for Wire-Bond
Packages (CS, FG, & BG)
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
B
B
B
B
ds031_66_112900
Bank 1
Bank 0
Bank 4
Bank 5
B
B
B
B