VLIW Microprocessor Hardware Design: For ASIC and FPGA

Chapter 4: FPGA Implementation

Figure 2.1 shows the design methodology flow for implementation of an ASIC design. Sections 3.4 to 3.12 in Chapter 3 describe the steps involved in synthesis to tapeout of an ASIC design. There is another alternative available to designers that do not wish to proceed with the ASIC path. Field-programmable gate array (FPGA) implementation is a different method of transforming the design into an IC device.

There are several reasons why some designers prefer FPGA implementation to ASIC implementation. Each has its own set of advantages and disadvantages and provides for very different cost structures. Section 4.1 describes the differences between FPGA and ASIC implementation.

4.1 FPGA Versus ASIC

An FPGA is an IC chip that allows designers to download their digital circuit into the IC chip and allows the IC chip to function as described by the downloaded digital circuit. A designer can design many different digital circuits and program these digital circuits into the FPGA. Among the many FPGAs that are available in the market are Altera, Xilinx, Actel and Atmel. FPGAs are programmable and allow for ease of configuration of digital circuits.

Conversely, an ASIC is an IC chip that specifically caters only to a digital circuit for which the ASIC chip was designed. Table 4.1 shows a detailed description of the advantages and disadvantages between each.

Table 4.1: Advantages and Disadvantages of FPGA and ASIC

FPGA

ASIC

FPGA can be reprogrammed to function as different digital circuits.

ASIC chip once fabricated can only be used...