Programming and Applications of the Lattice GAL22V10D-15LPN Generic PLD

The Lattice GAL22V10D-15LPN stands as a classic example of a Generic Programmable Logic Device (PLD) that has demonstrated remarkable longevity and utility in digital circuit design. As a 24-pin, electrically erasable CMOS device, it offers a flexible and cost-effective solution for implementing a wide range of combinatorial and sequential logic functions, effectively replacing multiple standard logic ICs with a single, programmable chip.

Architecture and Core Features

The "22V10" nomenclature defines its core architecture: 22 inputs and 10 output logic macrocells. Each output macrocell is connected to an I/O pin and is highly configurable, featuring a programmable architecture that includes a sum-of-products (SOP) logic array, a programmable register (D-type flip-flop), and multiplexers for controlling feedback and output polarity. The 15LPN suffix specifically indicates a 15ns maximum propagation delay (tPD) and a low-power operation, making it suitable for high-speed yet power-sensitive applications. The device is programmed using industry-standard hardware programmers and JEDEC fuse map files generated by logic compilers.

The Programming Workflow

Programming the GAL22V10D-15LPN follows a structured process. First, the desired logic function is described using a Hardware Description Language (HDL) like VHDL or Verilog, or more traditionally, schematic entry or Boolean equations. This design is then processed by PLD development software (e.g., WinCupl, Lattice ispLEVER) which performs synthesis, optimization, and fits the logic into the device's structure. The software generates a JEDEC file (JED), which is a textual representation of the fuse map—essentially a blueprint of which connections in the internal AND-OR array are to be made or broken. This JED file is then transferred to a universal programmer, which applies the necessary voltages to the chip to configure it electrically. A key advantage of this device is its electrically erasable (EECMOS) technology, allowing it to be reprogrammed thousands of times, which drastically accelerates prototyping and design iteration.

Diverse Application Fields

The programmability of the GAL22V10D-15LPN lends itself to a vast array of applications, often serving as a "glue logic" component that interfaces between larger, more complex devices.

Address Decoding: In microprocessor and microcontroller-based systems, it is exceptionally efficient for implementing complex memory and I/O address decoding logic, generating chip select (CS) signals based on specific address ranges.

State Machine Control: It is perfectly suited for implementing medium-complexity finite state machines (FSMs) that control the sequence of operations in digital systems, from simple timers to interface controllers.

Bus Interface and Protocol Logic: The device can be programmed to handle various bus arbitration, signal gating, and simple communication protocols, adapting different logic levels and timing requirements between system components.

Signal Conditioning and Pulse Generation: It can be used to create monostable multivibrators (one-shots), debounce circuits for mechanical switches, and generate clock pulses of specific widths with high precision.

System Integration: Its primary role is often to consolidate numerous discrete logic gates (e.g., 74-series TTL chips) into a single package. This reduces board space, component count, power consumption, and improves overall system reliability.

ICGOODFIND: The Lattice GAL22V10D-15LPN remains a quintessential and highly versatile PLD. Its enduring relevance is a testament to a well-designed architecture that balances speed, power, and flexibility. It excels in system integration, protocol bridging, and state machine control, offering a reliable and reprogrammable hardware solution that bridges the gap between fixed-function logic and high-density FPGAs. For engineers, it represents a fundamental tool for efficient and compact digital design.

Keywords:

Programmable Logic Device

Sum-of-Products (SOP)

Output Logic Macrocell

JEDEC File

Glue Logic