Introduction to FPGA main function modules (1)

The function of each module is as follows:

1. Programmable input and output unit (IOB)

The programmable input/output unit is referred to as the I/O unit, which is the interface part between the chip and the external circuit. It completes the driving and matching requirements of the input/output signals under different electrical characteristics. The schematic structure is shown in Figure 2-4. The I/O within the FPGA is categorized by group, and each group can independently support different I/O standards. Through the flexible configuration of the software, different electrical standards and I/O physical characteristics can be adapted, the driving current can be adjusted, and the upper and lower pull-down resistors can be changed. Currently, the frequency of I/O ports is getting higher and higher, and some high-end FPGAs can support data rates up to 2Gbps through DDR register technology.

IOB module

Figure 2-4 Internal structure of IOB

The external input signal can be input to the FPGA through the memory unit of the IOB module or directly into the FPGA. When an external input signal is input to the FPGA through the memory location of the IOB module, the hold time (Hold TIme) requirement can be reduced, usually by default to zero. In order to manage and adapt to various electrical standards, the IOB of the FPGA is divided into several banks. The interface standard of each bank is determined by its interface voltage VCCO. A bank can only have one type of VCCO, but VCCOs of different banks can different. Only ports of the same electrical standard can be connected together, and the same VCCO voltage is the basic condition of the interface standard. 2. Configurable logic block (CLB)

CLB is the basic logical unit within the FPGA. The actual number and characteristics of CLBs will vary from device to device, but each CLB contains a configurable switch matrix consisting of 4 or 6 inputs, some sizing circuits (multiplexers, etc.) and flip-flops. composition. The switch matrix is â€‹â€‹highly flexible and can be configured to handle combinatorial logic, shift registers or RAM. In Xilinx's FPGA devices, the CLB consists of multiple (typically four or two) identical slices and additional logic, as shown in Figure 2-5. Each CLB module can be used not only to implement combinatorial logic, timing logic, but also as distributed RAM and distributed ROM.

CLB structure diagram

Figure 2-5 Schematic diagram of a typical CLB structure

Slice is the basic logical unit defined by Xilinx Company. Its internal structure is shown in Figure 2-6. A slice consists of two 4-input functions, carry logic, arithmetic logic, storage logic and function multiplexer.

Typical 4-input Slice structure diagram

Figure 2-6 Schematic diagram of a typical 4-input Slice structure

The arithmetic logic consists of an exclusive OR gate (XORG) and a special AND gate (MULTAND). An XOR gate can enable a slice to achieve a 2-bit full-add operation. A dedicated AND gate is used to increase the efficiency of the multiplier. The carry logic is a dedicated carry signal. Compatible with function multiplexer (MUXC) for fast arithmetic addition and subtraction operations; 4 input function generator for 4 input LUT, distributed RAM or 16-bit shift register (Slice in Virtex-5 series chip) The two input functions are 6 inputs, which can implement a 6-input LUT or a 64-bit shift register. The carry logic includes two fast carry chains to improve the processing speed of the CLB module.

Water Dispenser

The water dispenser is a device that raises or lowers the temperature of barreled pure water (or mineral water) and is convenient for people to drink. Put bottled water on top of the machine and use it with bottled water. Water dispensers can be divided into three types: warm, ice, and ice. Ice heat machines are divided into semiconductor refrigerated water dispensers and compressor-type refrigerated water dispensers.

Among the many brands and models of water dispenser products, the water dispensers can be summed up as three types: warm, ice, and ice. The ice heater is divided into semiconductor refrigerated water dispensers and compressor-type refrigerated water dispensers. Deciding what type of water dispenser to buy is mainly based on the number of people drinking water and the cooling speed. As far as the cooling speed is concerned, under the same cooling time, the compressor-type refrigerated drinking water is much faster than the semiconductor refrigerated drinking water machine, and the supply of ice water is also more than the latter. Therefore, the compressor-type refrigerating water dispenser is suitable for occasions with a large number of people drinking water, such as group companies, institutions, conference rooms, office buildings, offices, bars, karaoke halls, etc. For units with a small number of people, hotel rooms and ordinary families, it is enough to buy a semiconductor refrigerated water dispenser.

It is quite important to consider purchasing water dispensers from the perspective of functional use. If you don`t like to use a water dispenser to make cold drinks, you can only use it for making tea and coffee every day. Just buy a warm water dispenser, which is practical and economical. If there are many young people, plus it is located in the southern tropical region, Those who have a higher usage rate in summer and like cold drinks should buy hot and cold water dispensers. In addition, there is also an ice-warming three-purpose machine, which can be selected according to needs.

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