FPGA architecture

In the market, FPGA architectures are available in different kinds of flavors. They are available for small applications and low cost to high performance with large number of gates. There are some FPGAs, which tend to bring in unique feature of low power and small form factor which makes them suitable for high speed mobile applications.

Most of the FPGA architectures have following common basic elements internally:

• Configurable Functional Elements 
• Input/Output Element
• DSP Elements
• Block RAM Elements
• PLL Elements

Configurable Functional Elements (CFE) is the basic building element for FPGA architecture, it has the capacity to implement both combinatorial or sequential Boolean function. To implement the combinatorial function it contains multiple inputs Look Up Tables (LUTs) and flip flops to realize sequential Boolean function. it may also contains various multiplexers to provide selectivity.

Input/Output Element (IOE) provides the logic to configure an FPGA pin as input, output or inout mode. At the time of assigning IOs to ports of a designs, users can also opt for IO standard (LVCMOS33, LVCMOS25, LVTTL33 etc.), driving strength etc. for the pins. 

DSP Elements (DSPE) has become essential part of an FPGA today. The reason is market driven, today most of the applications require DSP engine to process data digitally which provides predictable quality of results and performance. All communication and mobile application require this feature and so FPGAs are provide this elements internally.

Block RAM Elements (BRAME) makes an essential part of any digital logic design. Multiple block RAM elements are used as large RAM block in variety of configurable modes. Mostly all FPGAs provides capability to configure them as ROM as well which is useful.

PLL Elements Most of the applications today require more than one CLOCK sources with different frequency in a design. PLL elements help generate precisely different frequencies and phase matched with source as well. In addition to this, PLL elements can provide variety of other features like fine/coarse phase delay, frequency multiplication/division etc.

Besides these basic elements, FPGA also provides global buffer elements for clocking sources and a dedicated clocking network to minimize clock skew as well. This helps users to concentrate more on designing rather than worrying about skew and fan out capability of clocks.

In the market today, FPGAs from following manufacturers are available in a broad variety:

• Xilinx
• Altera
• Actel
• Lattice
• Achronix
• Silicon Blue

Readers are encouraged to go to their website and explore more, in case of any questions or discussion please leave a comment.