Lattice GAL16V8D-10QJ: Architecture, Key Features, and Typical Applications
The Lattice GAL16V8D-10QJ stands as a seminal device in the history of programmable logic. As a member of the Generic Array Logic (GAL) family, it provided a powerful, erasable, and reconfigurable alternative to fixed-function TTL logic and one-time programmable PAL devices. Its architecture and flexibility cemented its role as a fundamental building block in countless digital designs.
Architecture: A Look Inside
The GAL16V8D-10QJ is based on a programmable AND array feeding into a fixed OR array, a structure known as the PAL-like programmable architecture. The "16" in its name refers to the number of inputs, while the "V8" indicates it has eight output logic macrocells (OLMCs), offering significant versatility.
The core of its programmability lies in the AND array, which generates product terms. These product terms are then summed in the OR array to create specific sum-of-product logic functions. The true genius of the design is in the Output Logic Macrocell (OLMC). Each OLMC can be configured by the user to operate in several modes:
Combinational Mode: The output is solely a function of the current input state.
Registered Mode: The output is stored in a D-type flip-flop, synchronizing it to a clock signal, which is essential for state machines and counters.
Complex Mode: Allows for more sophisticated feedback and input/output configurations.
This reconfigurable macrocell architecture allowed a single GAL16V8D to replace a wide variety of standard logic ICs.
Key Features and Advantages
The GAL16V8D-10QJ's enduring popularity was driven by a set of powerful features:
High Performance: The "-10" suffix denotes a maximum propagation delay of 10 ns, making it suitable for high-speed applications.
Electrically Erasable (E²CMOS) Technology: Unlike its fusable-link predecessors, the GAL16V8D could be erased and reprogrammed hundreds of times. This drastically accelerated prototyping, debugging, and design iteration.
100% Testability: The internal logic functions could be thoroughly tested, ensuring high manufacturing yields and design reliability.
Ultra-Low Power Consumption: The advanced E²CMOS technology ensured very low static power dissipation, a critical feature for power-sensitive applications.
8 Output Logic Macrocells: The configurable OLMCs provided immense design flexibility from a single, standard chip.
Typical Applications
The GAL16V8D-10QJ found its way into a vast array of digital systems, primarily serving as a glue logic integrator. Its typical applications included:
Address Decoding: In microprocessor and microcontroller-based systems, it was extensively used to decode address buses and generate chip select signals for memory (RAM, ROM) and peripherals.
State Machine Design: The registered mode of its macrocells made it ideal for implementing finite state machines (FSMs) for control logic.
Bus Interface and Control: It was perfect for implementing custom timing and control signals for interfacing between different parts of a digital system, such as between a CPU and its peripheral chips.
Code Conversion and Data Gating: It efficiently handled tasks like converting between binary and Gray code or acting as a multiplexer/de-multiplexer.
The Lattice GAL16V8D-10QJ was more than just a chip; it was an enabler of digital innovation. Its reprogrammable nature, high speed, and flexible macrocell architecture democratized logic design, allowing engineers to consolidate complex TTL logic into a single, reliable, and field-updatable component. It laid the groundwork for the complex CPLDs and FPGAs that followed, leaving an indelible mark on the electronics industry.
Keywords:
Programmable Logic Device (PLD)
Output Logic Macrocell (OLMC)
Glue Logic
E²CMOS
Address Decoding
