Field Programmable Gate Arrays

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Field Programmable Gate Arrays (FPGAs) were the next step from CPLDs. Instead of a fixed array of gates, the FPGA uses the concept of a Complex Logic Block (CLB). This is configurable and allows not only routing on the device, but also each logic block can be configured optimally. A typical CLB is shown in Figure 2.3. This extreme flexibility is very efficient as the device does not rely on the fixed logical resources (as in the case of a CPLD),

Typical programmable logic device.png

but rather is able to define whichever logical functions are required as part of the logic block reconfiguration.

The CLB has a look-up table (LUT) that can be configured to give a specific type of logic function when programmed. There is also a clocked d-type flip flop that allows the CLB to be combinatorial (non-clocked) or synchronous (clocked), and there is also an enable signal.

A typical commercial CLB (in this case from Xilinx ® ) is shown in Figure 2.4 and this shows clearly the two 4 input LUTs and various multiplexers and flip flops in a real device. A typical FPGA will have hundreds or thousands of CLBs, of different types, on a single device allowing very complex devices to be implemented on a single chip and configured

Complex programmable logic device.png

FPGA complex logic block.png

Typical commercial CLB architecture.png

FPGA structure of CLB.png

easily. Modern FPGAs have enough capacity to hold a number of complex processors on a single device. The layout of a typical FPGA (in CLB terms) is shown in Figure 2.5. As can be surmised from this schematic, the FPGA has a level of complexity possible that is orders of magnitude more than typical CPLD devices. With the advent of modern digital CMOS processes down to 45nm or even 28nm and beyond, the integration of millions of logical elements is now possible and to a speed unimaginable a decade previously—making extremely high-performance devices now possible (even into the realm of Gb/s data rates).

XC4VLX25-10FFG676C

Manufacturer:Xilinx
FPGA Virtex-4 LX Family 24192 Cells 90nm Technology 1.2V 676-Pin FCBGA
Product Categories: FPGAs (Field Programmable Gate Array)

Lifecycle:Obsolete -

RoHS:

XC3S200A-4FGG320I

Manufacturer:Xilinx
FPGA Spartan-3A Family 200K Gates 4032 Cells 667MHz 90nm Technology 1.2V 320-Pin FBGA
Product Categories: FPGAs

Lifecycle:Active Active

RoHS:

XC3S200A-4VQG100I

Manufacturer:Xilinx
FPGA Spartan-3A Family 200K Gates 4032 Cells 667MHz 90nm Technology 1.2V 100-Pin VTQFP
Product Categories: FPGAs

Lifecycle:Active Active

RoHS:

XC17S40SO20C

Manufacturer:Xilinx
PROM Serial 321.6K-bit 5V 20-Pin SOIC
Product Categories: Memory - Configuration Proms for FPGA's

Lifecycle:Obsolete -

RoHS: No RoHS

XC17S40XLSO20C

Manufacturer:Xilinx
PROM Serial 323K-bit 3.3V 20-Pin SOIC
Product Categories: Memory - Configuration Proms for FPGA's

Lifecycle:Obsolete -

RoHS: No RoHS

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