XC2V8000-5BF957C Xilinx, Inc., XC2V8000-5BF957C Datasheet - Page 27

• Manufacturer Part Number: XC2V8000-5BF957C
• Description: Virtex-II 1.5V Field-Programmable Gate Array
• Manufacturer: Xilinx, Inc.

Virtex-II 1.5V Field-Programmable Gate Arrays
3-State Buffers
Introduction
Each Virtex-II CLB contains two 3-state drivers (TBUFs)
that can drive on-chip busses. Each 3-state buffer has its
own 3-state control pin and its own input pin.
Each of the four slices have access to the two 3-state buff-
ers through the switch matrix, as shown in
TBUFs in neighboring CLBs can access slice outputs by
direct connects. The outputs of the 3-state buffers drive hor-
izontal routing resources used to implement 3-state busses.
The 3-state buffer logic is implemented using AND-OR logic
rather than 3-state drivers, so that timing is more predict-
able and less load dependant especially with larger devices.
Module 2 of 4
20
Figure 26: Virtex-II 3-State Buffers
Switch
Matrix
Slice
Slice
TBUF
TBUF
S1
S0
Figure 27: 3-State Buffer Connection to Horizontal Lines
Switch
CLB-II
matrix
DS031_37_060700
Slice
Slice
S3
S2
Figure
Programmable
connection
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Four horizontal routing resources per CLB are provided for
on-chip 3-state busses. Each 3-state buffer has access
alternately to two horizontal lines, which can be partitioned
as shown in
to SelectRAM memory and multiplier or I/O blocks are
skipped.
Number of 3-State Buffers
Table 11
each Virtex-II device. The number of 3-state buffers is twice
the number of CLB elements.
Table 11: Virtex-II 3-State Buffers
XC2V40
XC2V80
XC2V250
XC2V500
XC2V1000
XC2V1500
XC2V2000
XC2V3000
XC2V4000
XC2V6000
XC2V8000
Switch
matrix
CLB-II
Device
shows the number of 3-state buffers available in
Figure 27
3-State Buffers
. The switch matrices corresponding
per Row
3 - state lines
DS031_09_032700
112
144
176
208
16
16
32
48
64
80
96
DS031-2 (v1.8) October 12, 2001
Advance Product Specification
of 3-State Buffers
Total Number
11,520
16,896
23,296
1,536
2,560
3,840
5,376
7,168
128
256
768
R