Lattice LC4064C-25T48C: A Comprehensive Technical Overview of the CPLD

The Lattice LC4064C-25T48C represents a classic and highly capable implementation of a Complex Programmable Logic Device (CPLD) from Lattice Semiconductor's high-performance ispMACH 4000 family. Designed for a wide array of general-purpose logic integration tasks, this device combines a robust architecture with in-system programmability, making it a enduring choice for glue logic, address decoding, state machine control, and interface bridging in countless electronic systems.

Core Architectural Features

At the heart of the LC4064C lies a deterministic, fast-path CPLD architecture. Its structure is based on a Programmable Interconnect Matrix (PIM) that links multiple Generic Logic Blocks (GLBs). This design is fundamentally different from the granular architecture of FPGAs, resulting in predictable timing and superior pin-to-pin performance for wide fan-in combinatorial functions.

The device designation provides key specifications: "4064" indicates it contains 64 macrocells, which are the fundamental building blocks for creating logic functions. The "-25" suffix denotes a maximum pin-to-pin delay of 5.0 ns, enabling high-speed operation with a system frequency exceeding 125 MHz. The "T48C" identifies the package as a 48-pin Thin Plastic Quad Flat Pack (TQFP), a surface-mount package ideal for space-constrained applications.

Key Technical Specifications

Density: 64 Macrocells.

Speed: 5.0 ns maximum pin-to-pin propagation delay (tPD).

I/O Count: Up to 36 user I/O pins in the 48-pin package.

Voltage: Operates on a 3.3V core voltage with 3.3V, 2.5V, or 1.8V I/O compatibility, facilitated by its LVCMOS and LVTTL compatible I/Os. This makes it suitable for mixed-voltage environments.

Programmability: Features In-System Programmability (ISP) through a standard 4-wire JTAG (IEEE 1149.1) interface. This allows for programming and reprogramming of the device after it has been soldered onto a printed circuit board (PCB), vastly simplifying prototyping and field upgrades.

Power Management: The ispMACH 4000 architecture incorporates advanced power-saving features, making it suitable for power-sensitive applications.

Design and Development Ecosystem

Developing with the LC4064C is supported by Lattice's design software suite, ispLEVER (now superseded by Lattice Diamond and Lattice Radiant, which retain backward compatibility). This environment provides a complete flow from design entry (schematic or HDL like VHDL/Verilog), through synthesis, functional simulation, fitting, and timing analysis, to finally generating a JEDEC file for device programming.

Target Applications

The deterministic timing and instant-on characteristics of the LC4064C CPLD make it ideal for numerous functions, including:

Address decoding in microprocessor and microcontroller systems.

Bus interface logic and protocol bridging (e.g., between PCI and a local bus).

State machine implementation for system control.

I/O expansion and signal gating.

Clock management and division.

Advantages and Considerations

The primary advantage of choosing a CPLD like the LC4064C over a larger FPGA or a multitude of discrete logic ICs is its design integration and flexibility. It reduces board space, component count, and overall system cost while providing the ability to change logic functions without altering the physical PCB. Its non-volatile configuration memory means it boots instantly upon power-up, unlike many SRAM-based FPGAs that require an external configuration device.

However, for today's designs, it is considered a smaller-capacity device. It is less suited for highly complex algorithms, large memory blocks, or processor implementations, which are the domain of modern FPGAs and SoCs.

ICGOODFIND: The Lattice LC4064C-25T48C remains a quintessential CPLD, valued for its high-speed deterministic performance, 3.3V core with multi-voltage I/O support, and robust in-system programmability. It perfectly embodies the CPLD's role as a flexible and reliable workhorse for system integration and control logic, bridging the gap between discrete logic and high-density FPGAs.

Keywords: CPLD, In-System Programmability (ISP), Macrocell, Pin-to-Pin Delay, 3.3V Core.