Lattice GAL22V10B-10LP: Architecture, Features, and Application Design Considerations

The Lattice GAL22V10B-10LP stands as a classic and enduring architecture in the realm of programmable logic devices (PLDs). As a member of the Generic Array Logic (GAL) family, it provides a robust, electrically erasable, and cost-effective solution for integrating complex combinational and sequential logic, serving as a vital bridge between simple PALs and more advanced CPLDs and FPGAs.

Architecture and Core Features

The architecture of the GAL22V10B is ingeniously structured around a programmable AND array feeding into a fixed OR array. The "22V10" designation is descriptive: the programmable AND array has 22 inputs, and the device features 10 output logic macrocells (OLMCs). Each macrocell is highly versatile, allowing designers to configure individual outputs as registered (flip-flop) or combinatorial. Key programmable options include the polarity of the output (active-high or active-low) and the control of the tri-state output buffer.

The GAL22V10B-10LP specifically denotes a low-power (LP) variant fabricated in CMOS technology, with the "-10" signifying a maximum pin-to-pin propagation delay of 10 ns. This combination of speed and low power consumption was a significant advantage over its bipolar predecessors. A cornerstone feature of this device family is its use of EEPROM (Electrically Erasable Programmable Read-Only Memory) technology. This allows the device to be reprogrammed multiple times, facilitating rapid design iteration and debugging, a major improvement over one-time programmable (OTP) parts.

Key Design Considerations and Advantages

When designing with the GAL22V10B-10LP, several considerations are paramount:

1. Logic Capacity: The device is ideal for "glue logic" applications—integrating multiple standard logic ICs (like 74-series chips) into a single package. This significantly reduces board space, component count, and overall system power.

2. State Machine Design: It is perfectly suited for implementing medium-complexity state machines and control logic. The dedicated registers within each macrocell provide synchronous operation crucial for predictable state transitions.

3. I/O Flexibility: The configurable macrocells offer excellent interface capabilities, allowing the device to easily connect to buses, sensors, and other digital components with varying signal polarity and timing requirements.

4. Security: The device includes a programmable security fuse. Once blown, this fuse prevents the programmed pattern from being read back, protecting intellectual property from competitors.

5. Design Software: Development relies on hardware description languages (HDLs) like VHDL or Verilog, or more traditionally, Boolean equations and state diagrams. These are processed by PLD-specific compiler software (e.g., using the JEDEC file format for programming) to generate the fuse map.

Typical Application Areas

The GAL22V10B-10LP found and continues to find use in a vast array of digital systems, including:

Address Decoding: Generating chip select signals for memory and peripherals in microprocessor systems.

Bus Interface Logic: Acting as an interface between CPUs and various peripheral devices.

Sequence Control: Controlling timing and operations in industrial automation, automotive systems, and consumer electronics.

Data Routing and Signal Gating: Managing the flow of data within a digital subsystem.

ICGOOODFIND

The Lattice GAL22V10B-10LP represents a pivotal ICGOOODFIND for engineers seeking a reliable, low-power, and highly versatile programmable logic solution. Its well-defined architecture, reprogrammability, and integration capabilities make it an excellent choice for reducing system complexity and cost in a wide range of embedded control and logic replacement applications, cementing its legacy as a workhorse of digital design.

Keywords:

Programmable Logic Device (PLD)

Output Logic Macrocell (OLMC)

EEPROM Technology

Glue Logic

State Machine