Overview of Programmable Logic Devices

These are devices that are used in electronic circuits to make reconfiguration of the same possible. The logical gates that are normally used perform a fixed function however, the Programmable Logic Devices (PLD) does not perform any predefined task when they are manufactured and need to be programmed before they can be used. Before the introduction of PLDs, ROM (Read Only Memories) was used. EPROM that was available could be programmed by using any standard hardware for that device and hence, did not require any other peripheral hardware. Another advantage of ROMs is that a particular binary code stored in it could be obtained on any of the n output lines that were available in it. Thus, they can be programmed in any way one wishes to. However, ROMs have some disadvantages when they are used as PLDs. They do not produce the outputs as quickly as other devices; they…

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Kick start guide to start working with Programmable Logic Devices from Altera

Probably everyone knows what are logical IC’s and how to use them in the design. But if design is more complex, electronics enthusiasts more likely are going to choose microcontrollers as they minimizes the count of external components. But problem is that not everything is possible with microcontrollers. They have many disadvantages when fast response to input signals is needed. Microcontrollers execute operations one by one in sequence (conveyor). So output result will occur after some number of clock cycles. One way is to use hard logic IC’s. But when complexity grows – number of IC packages also increases. This way design board becomes tremendous. So where programmable logic devices (PLD) comes to help. CPLD devices have a number of base elements (gates) without strict electrical interconnection. So designer can program these connections to combine any logical combination. Programmable logical devices allow to construct any logical device including counters, triggers…

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Programmable logic devices

In a market you can find a bunch of programmable logic devices – PLD. They can be small scale integrated – SSI, medium scale integrated- MSI, mask programmed gate array – MPGA (MPGD – masked programmable logic devices). Now the most popular are FPGA (Field Programmable Gate Arrays). What is a difference between FPGA and MPGA? MPGA are hard-coded during manufacturing and cannot be erased or reprogrammed while FPGA are programmable – usually EEPROM or SDRAM. Of course there are other differences between FPGA and MPGA. One of them is speed. MPGA usually is faster as MPGA needs fewer elements to form logic gate while FPGA needs additional elements to enable programmability – this adds additional resistances and capacitances in circuits. But today’s technology allows reaching significant speeds with FPGAs too. Other difference may be integration. As we mentioned MPGA requires fewer elements to form one logical gate, they can…

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