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Author: Admin | 2025-04-28
Programmable Logic Devices (PLDs) are electronic devices that can be programmed to perform various digital logic functions. GALs, or Generic Array Logic devices, are a type of PLD developed by Lattice Technology. They are well suited for small-scale designs and replace older PAL devices.GALs are flexible devices, as they can perform a combination of logical functions like AND, OR, and NAND gates and registered logic functions like counters and shift registers, all on the same chip. They are also reprogrammable, making it easy to correct design errors or adjust the board layout.GALs and PALs were famous in the past but have been replaced by newer PLDs like FPGA and CPLD. GALs are still available and used in older electronic designs and applications that do not require advanced functionality or many resources.What is the difference between PAL and GAL?Both Programmable Array Logic (PAL) and Generic Array Logic (GAL) are programmable logic devices (PLDs), but there are significant differences between the two.PAL Devices:PAL devices were one of the first types of PLDs to be developed. They are used to implement simple digital logic circuits and are typically used to replace individual logic devices such as AND gates, OR gates, and flip-flops. PAL devices are typically programmed using a PAL-specific programming language, and once programmed, they can perform the functions of multiple individual logic devices.PAL devices are an older technology, simple, and use one-time programmable technology, typically used for replacing a few gatesGAL Devices: On the other hand, GAL devices are a more advanced type of PLD. They are similar to PAL devices but are more flexible and can implement more complex digital logic circuits. GAL devices can be programmed using a hardware description language (HDL) such as VHDL or Verilog, which allows for a more efficient and powerful description of the logic circuit. GAL devices can be reprogrammed multiple times, unlike PAL, which is one-time programmable.GAL devices are newer, more flexible, and contains reprogrammable technology. GAL devices can be implemented in more complex digital circuits.GAL Device ArchitectureThere were several varieties of GAL devices. The GAL16V8 device from Lattice Technology in figure 1 is the focus of this post. Simple to design equations around this chip, a similar IC is the GAL20V8 from Lattice.The old-school GAL16V8A device is commonly packaged in a standard 20-pin DIP IC socket and is 0.3 inches wide.Figure 1Pins 12 to 19 are each connected to Output Logic Macro
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