Lattice GAL26CV12B-15LJN: A Comprehensive Technical Overview of the CPLD

The Lattice GAL26CV12B-15LJN represents a specific implementation of a Complex Programmable Logic Device (CPLD) from Lattice Semiconductor's classic Generic Array Logic (GAL) family. This device, packaged in a 28-lead PLCC (Plastic Leaded Chip Carrier), is engineered to provide a flexible and reliable solution for a wide range of glue logic, state machine, and address decoding applications. Its architecture is a direct evolution of the foundational PAL (Programmable Array Logic) and GAL devices, offering enhanced features and electrically erasable (E²) reprogrammability.

Core Architecture and Key Features

At the heart of the GAL26CV12B lies a structured logic array. The "26V12" designation indicates its lineage and core capability: it features a programmable AND array feeding into fixed OR terms, which are then routed through Output Logic Macro Cells (OLMCs). The OLMCs are a critical component, providing the user with configurable output structures. Each of the 12 outputs can be individually programmed to be combinatorial or registered (clocked), and set for active-high or active-low operation. This configurability allows the same silicon device to implement a vast array of logic functions.

A key advancement in this series, denoted by the 'V' (for versatile), is the inclusion of a programmable output polarity. This feature simplifies logic design by allowing the inversion of output signals in software, often eliminating the need for external inverters. The device also incorporates a dedicated clock pin (CLK) and an output enable (OE) pin, providing central control for synchronous operations and three-state output management.

The "-15" suffix in the part number specifies the maximum propagation delay (tPD) of 15 nanoseconds, making it a component suited for systems with moderate speed requirements. The "LJN" suffix details the package (PLCC), temperature grade (Commercial, 0°C to +75°C), and other manufacturing specifics.

In-System Programmability and Design

A significant advantage of the GAL26CV12B over its one-time programmable (OTP) PAL predecessors is its use of E²CMOS (Electrically Erasable CMOS) technology. This allows the device to be reprogrammed thousands of times, drastically accelerating the development cycle, prototyping, and field updates. Designers use Hardware Description Languages (HDLs) like VHDL or Verilog, or simpler schematic entry, within logic design software to create a logic configuration. This design is then compiled into a JEDEC file, which is transferred to the device using a universal programmer.

Target Applications

The GAL26CV12B-15LJN excels in integrating multiple simple-to-medium complexity TTL (Transistor-Transistor Logic) devices into a single chip. Its typical applications include:

Address Decoding: Generating chip select signals for microprocessors and microcontrollers.

State Machine Control: Implementing finite state machines for system management.

Bus Interface Logic: Acting as an interface between processors and peripherals with different timing requirements.

Data Routing and Gating: Managing data flow across different system buses.

Conclusion and ICGOODFIND Summary

The Lattice GAL26CV12B-15LJN stands as a robust and highly versatile workhorse in the world of digital logic. While newer, larger CPLDs and FPGAs have taken over more complex tasks, this device remains a perfect fit for applications requiring integration of discrete logic, simple state machines, and fast I/O response. Its reprogrammability, predictable timing, and familiar architecture make it a enduring choice for engineers designing and maintaining a vast array of electronic systems.

ICGOODFIND: The Lattice GAL26CV12B-15LJN is a classic E²CMOS-based CPLD valued for its 12 configurable macro cells, 15ns speed performance, and role in effective system integration and logic consolidation.

Keywords:

1. CPLD (Complex Programmable Logic Device)

2. E²CMOS (Electrically Erasable CMOS)

3. Programmable Logic

4. Output Logic Macro Cell (OLMC)

5. JEDEC File