Types of ASICs

The following types of ASICs are currently often mentioned:

• Standard cell based ASIC is probably the most generic type of ASIC nowadays. This type of ASIC is constructed from the cell library usually provided by the semiconductor fabrication plant (or foundry). The set of standard cells is automatically synthesized from the RTL description on VHDL or Verilog.
• Full-custom ASIC differs from the previous type of ASIC in that the ASIC designer designs some logic cells and/or layout specifically for this ASIC. Some of the cells can still be taken from the library. This approach has to be used when the standard library doesn't contain some specific cells or when the standard cells don't meet some specific requirements on performance, area or power dissipation.
• Structured ASIC is quite a different term that shouldn't be confused with the previous ones. This term is usually used in connection with ASICs built on basis of FPGA. Major FPGA vendors can produce chips pre-configured with customer's FPGA bitstream, for the price a few times lower than that of FPGA. The design costs are thereby similar to the design costs for FPGA projects. This can be a cost-effective solution for medium-volume products. This technique is implemented by Xilinx under the brand EasyPath and by Altera under the brand HardCopy.

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