Top 10 Programmable Logic articles of 2012

http://www.eetimes.com/design/programmable-logic/4403530/Top-10-Programmable-Logic-articles-of-2012?pageNumber=0&Ecosystem=programmable-logic

All about FPGAs

by Bob Zeidman

Emerging technologies

Cores: When I talk about a "core" I am simply referring to a large self-contained function. There are two basic types of cores. The soft core, known as an IP core, is a function that is described by its logic function rather than by any physical implementation. Soft cores usually consist of hardware description language (HDL) code. Hard cores, on the other hand, consist of physical implementations of a function. With respect to FPGAs, these hard cores are known as embedded cores because they are physically embedded onto the chip die and surrounded by programmable logic.

Many FPGA vendors have begun offering cores. The density of programmable devices is increasing, enabling what is called a Programmable System on a Chip (PSOC). Whereas programmable devices were initially developed to replace glue logic, entire systems can now be placed on a single programmable device. SOCs include of all kinds of complicated devices, like processors. In order to place these complex functions within a programmable device, there are three options: the first is to either (a) design the function yourself and place it in the programmable logic, (b) purchase the HDL code for the function and incorporate it into your HDL code, or (c) get the vendor to include the function as a cell embedded in the programmable device. The second option is the IP core or soft core, while the third option is the embedded core or hard core.

IP Cores: IP cores are often sold by third party vendors that specialize in creating these functions. Recently, FPGA vendors have begun offering their own soft cores. IP cores reduce the time and manpower requirements for the FPGA designer. IP cores have already been designed, characterized, and verified. Also, IP cores can often be modifiable, meaning that you can add or subtract functionality to suit your needs. They are also portable from one vendor to another.

But IP cores may also be expensive. Electrical characteristics such as timing or power consumption for IP cores can be optimized to a limited degree, but the actual characteristics depend on its use in a particular device and also depend on the logic to which it is connected. IP cores purchased from a third party may not be optimized for your particular FPGA vendor's technology. You may not be able to meet your speed or power requirements, especially after you have placed and routed it.

Embedded Cores: The embedded core is ideal for many users, which is one reason why programmable device vendors are now offering embedded cores in their devices. The embedded core will be optimized for the vendor's process to give you good timing and power consumption numbers. The function will be placed as a single cell on the silicon die and so the performance of the function will not depend on the rest of your design since it will not need to be placed and routed.

Some embedded cores are analog devices that cannot be designed into an ordinary FPGA. By integrating these functions into the device, you can avoid the difficult process of designing analog devices, and you save the chips and components that would otherwise be required outside the programmable device.

Of course there is a drawback to embedded cores. By using an embedded core in your programmable device, you tie your design into a single vendor. Unless another vendor offers the same embedded core, switching to another vendor will require a large effort and will not be pleasant.