September 18, 1996 (Version 1.04)
4-7
Note:
1. Most functions are faster in XC4000EX due to faster carry logic, direct connects, and other additional interconnect.
Taking Advantage of Reconfiguration
FPGA devices can be reconfigured to change logic function
while resident in the system. This capability gives the sys-
tem designer a new degree of freedom not available with
any other type of logic.
Hardware can be changed as easily as software. Design
updates or modifications are easy, and can be made to
products already in the field. An FPGA can even be recon-
figured dynamically to perform different functions at differ-
ent times.
Reconfigurable logic can be used to implement system
self-diagnostics, create systems capable of being reconfig-
ured for different environments or operations, or implement
multi-purpose hardware for a given application. As an
added benefit, using reconfigurable FPGA devices simpli-
fies hardware design and debugging and shortens product
time-to-market.
Table 2: Density and Performance for Several Common Circuit Functions in XC4000E
1
Design Class
Function
CLBs Used
XC4000E-3
XC4000E-2
Units
Memory
256 x 8 Single Port (read/modify/write)
72
63
80
MHz
32 x 16 bit FIFO
simultaneous read/write
MUXed read/write
48
32
63
63
80
80
MHz
MHz
Logic
9 bit Shift Register (with enable)
5
170
200
MHz
16 bit Pre-Scaled Counter
8
142
170
MHz
16 bit Loadable Counter
8
65
76
MHz
16 bit Accumulator
9
65
76
MHz
8 bit, 16 tap FIR Filter sample rate
parallel
serial
400
68
55
8.1
65
10
MHz
MHz
8 x 8 Parallel Multiplier
single stage, register to register
73
37
30
ns
16 bit Address Decoder (internal decode)
3
4.7
3.9
ns
9 bit Parity Checker
1
4.3
2.7
ns
