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PLD definition

(Programmable Logic Device-Programmable Logic Device).A PLD is an electronic component used for the manufacture of reconfigurable digital circuits.

Unlike the logic gates, which have a fixed function, a PLD has an undefined function at the time of manufactured.Before a PLD can be used in a circuit, it can be programmed, that is, reconfigured.

Current PLDs use different ways of storing data: silicon antifusibles, SRAM, EPROM cells or EEPROM and Flash memory.

Before PLD

Before PLD devices were invented, ROM memory chips (PROM, EPROM, EEPROM) were used to create logical functions Arbitrary combinations of M inputs with N outputs, this being the best general purpose combinational logic device available at the time, but they are slower circuits than dedicated logic circuits, they may not work well in asynchronous logic transitions They consume a lot of energy, are more expensive, etc.They also do not have input or output records, so they cannot be used independently for sequential logic (external TTL registers were often used).

as for the programming languages ​​used, PALASM and ABEL for low complexity devices, while Verilog and VHDL are popular languages ​​for complex devices.

Programming devices (See programmer (hardware)) are used to transfer Boolean logic patterns within a programmable device.Universal programmers are currently used to support various families of logical devices from different manufacturers.Some typical formats used to store Boolean logic patterns are JEDEC, Altera POF (Programmable Object File) or Xilinx BITstream.

The first PLD

The first programmable logic devices were presented by Motorola (the XC157 in 1969), Texas Instruments (the TMS20 00 in 1970, based on IBM's read-only ROAM memories, could be programmed by altering the metal layer during the production of the integrated circuit.) This company started calling them "programmable logic devices" (Programmable Logic Array).

In 1973 National Semiconductor introduced the DM7575, with 14 inputs and 8 outputs without memory records; This device was the basis of the 82S100, produced by Signetics in 1975.

The General Electric company was the first to create a PLD device that could be deleted: it launched in 1974, together with Monolithic Memories, the PALA ( Programmable Associative Logic Array).

Featured PLD devices

* PAL (Programmable array logic) * GAL (Generic array logic) * CPLD * FPGA

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