Lattice ISPLSI2064A: Architecture, Design Applications, and System Integration
The Lattice ISPLSI2064A stands as a pivotal component in the history of programmable logic, representing a high-density, high-performance Complex Programmable Logic Device (CPLD) from the in-system programmable (ISP) era. Its architecture was engineered to bridge the gap between simple PALs/GALs and more complex FPGAs, offering a balanced mix of density, speed, and flexibility for a wide array of digital design applications.
Architectural Overview
At the core of the ISPLSI2064A's architecture is a programmable, high-density logic array structured around a Global Routing Pool (GRP). This GRP acts as a central switchboard, interconnecting all internal elements. The device features 64 Universal Logic Blocks (GLBs), each containing programmable AND/OR arrays and macrocells. This structure allows for the efficient implementation of complex combinatorial and sequential logic functions.
A key feature of this family is its in-system programmability (ISP), enabled through an IEEE 1149.1 (JTAG) interface. This allows for the programming and reprogramming of the device after it has been soldered onto a printed circuit board (PCB), drastically simplifying the prototyping process and enabling field upgrades. Furthermore, the architecture incorporates dedicated I/O cells that provide programmable bus maintenance and pin-to-pin logic delays as low as 7.5 ns, ensuring high-speed performance for critical interfaces.
Design Applications
The combination of density (approximately 1000 PLD gates) and speed made the ISPLSI2064A exceptionally versatile. Its primary applications included:
Glue Logic Integration: A primary use case was the consolidation of numerous discrete TTL logic chips and smaller PLDs into a single, compact CPLD. This significantly reduced board space, component count, and overall system cost while improving reliability.
State Machine Control: The predictable timing and deterministic performance of its programmable logic made it an ideal platform for implementing complex finite state machines (FSMs) that controlled system operations.
Address Decoding and Bus Interface: In microprocessor and microcontroller-based systems, it was extensively used for generating chip-select signals, managing wait states, and implementing custom bus arbitration logic.
Protocol Bridging and Data Path Control: The device was often employed to manage data flow and translate between different communication protocols (e.g., between parallel and serial interfaces), acting as a vital communication bridge.
System Integration
Integrating the ISPLSI2064A into a electronic system was streamlined by its ISP capability. Designers could use hardware description languages (HDLs) like VHDL or Verilog, or schematic entry within Lattice's design software suite, to create the device's logic. After synthesis and place-and-route, the generated JEDEC file was transmitted to the CPLD via the standard JTAG port using a simple programming cable.
This ease of integration allowed for rapid design iterations. A flaw in the logic could be corrected by modifying the source code and reprogramming the device in-circuit, eliminating the need for physical chip replacement. This accelerated development cycles and provided a significant advantage in time-to-market for products ranging from networking equipment and telecommunications hardware to industrial control systems and advanced test instruments.
The Lattice ISPLSI2064A was a cornerstone CPLD technology that empowered a generation of digital designers. Its robust, predictable architecture and revolutionary in-system programmability provided a critical stepping stone, enabling higher integration, faster development, and more reliable systems. It effectively demonstrated the transition towards a fully programmable system-on-chip paradigm.
Keywords:
1. In-System Programmable (ISP)
2. Complex Programmable Logic Device (CPLD)
3. Glue Logic Integration
4. JTAG Interface
5. Deterministic Timing
