ABSTRACT
This chapter focuses on various hardware implementation technologies and the advantages and disadvantages of each. It provides an overview of the technologies behind historical and modern programmable logic devices. Field programmable logic is often contrasted to general-purpose microprocessors as a way of obtaining fast, low power consumption and flexible implementations of particular algorithms. However, the automation tools that exist for hardware design are currently not at the comparatively advanced stage of optimising software compilers. Network intrusion detection systems typically take advantage of the hardware-efficiency of detecting the regular expressions corresponding to known attacks. Programmable logic devices have long been used for prototyping application specific integrated circuit designs, and are fast becoming the medium of choice for small to medium end-product production runs. The main logic element used in commercial devices is based on a small read-only memory with four address lines and one data line, known as a 4-input lookup table, or 4-look-up table.
