There are two ways to calculate the number:
The first is to compare the FPGA basic unit (such as LUT FF, ESB\/BRAM) with the standard gate array that realizes the same function, the number of gates contained in the gate array is the equivalent number of gates of the FPGA basic unit, and then multiply the number of basic units to get the FPGA gate estimate.
The second is to use FPGA and standard gate array respectively to achieve the same function, from which the equivalent gate number of FPGA can be calculated. This method relies more on empirical data.
For the first method, FPGA includes resources such as LUT\/FF\/RAM, and when analyzing the equivalent number of various resources, the general principle is the equivalent principle, that is, to achieve the same function, and the number of gates required in the standard gate array is the equivalent number of resources in the FPGA.
For example, to achieve a 4-input XOR with register output, in the FPGA need to use a LUT and a FF implementation, in the standard gate array generally to use 21 and not gate implementation, so 1 LUT+1 FF is equivalent to 21 gates.
For ESB (BRAM), 4 gates are generally required when implementing 1bit RAM with standard gate array, so when ESB\/BARM is used as RAM, 1bit is equivalent to 4 gates. A 2048Bit ESB in the FPGA, the equivalent number of gates is 8K.
The equivalent gate number of FPGA can not be calculated accurately by these data alone. Because this is a simple case, the reality is much more complicated.
Logic gate is the basic component of logic circuit, can be composed of transistors, logic gate can be roughly divided into basic gate, universal gate and extension gate three kinds, of which the basic door can be divided into and gate, or gate and non-gate three kinds. The logic gate can convert the high and low levels of the signal into the logical signal of response, so as to realize the logical operation.
A number of active devices and passive devices and their connections are made on a semiconductor substrate according to certain functional requirements, such a product is called an integrated circuit. If the function it completes is a logical function or a digital function, it is called a digital integrated circuit. The simplest digital integrated circuit is the integrated logic gate.