Intro to programmable logic/ Devices Programmablelogic devices are one of the electronic devices that used to build andconfigure the Digital circuit. Compare to logic gate, this is undefinedfunction at the time of manufacture. First Programmable logic was introduced at the time of 1969. Itwas founded by Motorola, known as XC-157.This is composed of 12gates and 30 uncommitted input oroutputs.
After that, Texas instruments made another new programmable logic that programmable IC.This is based on IBM-read associative with Memory or ROM. This device is known as the TMS 2000.This device is composed of 17 inputs and 18 outputs with 8 JK flip flop for memory. In 1971, Companyknows as General Electric founded new programmable logic device. This experimental device improvedon IBM’s ROAM with allowing multilevel logic.
In 1973 National Semiconductor introduced a PLAdevice with 14 inputs and 8 outputs with no memory registers. There are variousadvantages that programmable logic devices have. First, There is no need forthe time-consuming logic design of random-logic gate. This makesprogram quicker than just wiring bunch of electronic circuit with complex system.
Second,checking the design is easy, and change the design is also easy. Third, Layout is far simpler than thatfor random-logic gate. So, it is less time-consuming. Fourth, PLA is a very inexpensive approach,greatly shortening designing time. PLAs have the following disadvantages compared with random-logic gatenetworks. There are severaldisadvantages of the programmable logic devices. First, for storing the same function or tasks, PLAs can be smaller than ROMs. Second, Designand the layout of random-logic gate networks are far more tedious and time- consuming.
Also, there aremany different types of logic devices. First, I want to talk about SPLD. Thisis simplest, and smallest, and not much expensive form of programmablelogic device. This is very similar to a Complex form, but an SPLD will have less IO pins and programmablecomponents, consumes less Power and requires special programming device to figure out.This is non-volatile and remaining their state after power is removed. Microchip SPLD products consist of industrystandard 16V8 and 22V10s in a variety of voltage. They typically composed of 4 to 22fully connected macro-cells. These macro-cells typically composed of some combinatorial logic like And /ORgate.
It used in boards to change the standard basic logic of And/OR gate. Another uniquetype of programming logic devices are known as the CPLD. It stands for complex programmable logic device. It is device that have the architecturalfeatures of both, PALS and FPGAs. CPLD is composed of two features. Non-volatile memory, andlegacy CPLD devices. CPLD is an evolutionary step from even smaller devices than PLAs. The maindistinction between FPGA and CPLD device architectures is that FPGAs are internallybased on look-up tables.
FPGA is stands for field-programmable gate array. This is anintegrated circuit designed to be configured by a customer or a designer aftermanufacturing – hence “field-programmable”. This is composed of array ofprogrammable logic blocks.
Logic blocks exist to perform complex combinational functions, simply logic gates like AND/XOR.This device trying to implement complex digital computations. Examples are PAL known as programmablearray logic, General array logic, Programmable logic array, programmable logic device.
Most important feature of SPLD is macro-cell.Macro-cell is fully connected to the others inthe device. Some of SPLDs use either fuses or non-volatile memory cells such as EPROM, EEPROM, or FLASH todefine the functionality. Most SPLD’s are used within EPROM, EEPROM, or FLASH to define thefunctionality. CPLD is compose ofthe two to 64 SPLDs.
CPLD composed of tens to a few hundred macro-cells.