Lattice Semiconductor ISPLSI1016E-125LTN44: A Comprehensive Technical Overview of the High-Density CPLD

The Lattice Semiconductor ISPLSI1016E-125LTN44 stands as a quintessential representation of a high-density Complex Programmable Logic Device (CPLD) from a pioneering era of programmable logic. This device, part of the renowned ispLSI 1000E family, was engineered to bridge the gap between simple PALs/GALs and larger FPGAs, offering a balanced mix of density, performance, and in-system programmability (ISP) that made it a popular choice for a wide array of digital logic applications.

Architectural Foundation: The Generic Logic Block (GLB)

At the core of the ISPLSI1016E's architecture is its high-density, electrically erasable and reprogrammable logic structure. The device is built around a series of Generic Logic Blocks (GLBs), which are the fundamental programmable units. Each GLB contains programmable AND/OR arrays and configurable registers, allowing it to implement a variety of combinatorial and sequential logic functions. The ISPLSI1016E contains 16 of these GLBs, providing a substantial amount of logic resources for its class.

Global Routing Pool (GRP) and I/O Flexibility

A key feature enabling the high-density integration is the Global Routing Pool (GRP), a centralized interconnect resource that provides 100% routability between all GLBs. This architecture eliminates the routing bottlenecks often found in earlier PLDs, ensuring that design changes do not compromise performance or utilization. The device is housed in a 44-pin TQFP (Thin Quad Flat Pack) package, offering 32 dedicated I/O pins. These I/O pins are connected to programmable I/O cells that support a wide range of voltage levels and interface standards, including TTL and LVCMOS, making it highly versatile for interfacing with other system components.

In-System Programmability (ISP)

A defining characteristic of this device is its industry-leading In-System Programmability (ISP). Utilizing a simple 5-wire interface (SDI, SDO, SCLK, MODE, and ispEN), the device can be reprogrammed after being soldered onto a printed circuit board (PCB). This capability drastically simplifies the prototyping process, field upgrades, and design iterations, reducing both time-to-market and manufacturing costs.

Performance and Key Specifications

The part number suffix "-125LTN44" provides critical performance and package information:

-125: Denotes a maximum pin-to-pin delay of 12.5 ns, enabling system clock frequencies to operate comfortably up to 90 MHz. This speed was more than adequate for implementing complex state machines, address decoders, and bus control logic in contemporary microprocessor systems.

L: Indicates it is a low-power (3.3V) device, a significant advantage for power-sensitive designs.

TN44: Specifies the 44-pin TQFP package.

The device offers 1000 PLD gates and features non-volatile E²CMOS® technology, meaning the programmed design is retained even when power is removed.

Target Applications

The combination of density, speed, and ISP made the ISPLSI1016E-125LTN44 ideal for a broad spectrum of applications, including:

System-level integration (glue logic replacement)

Bus interfacing and protocol bridging (e.g., PCI to local bus)

Dedicated control logic and state machines

Address decoding and memory control

Communication and networking equipment

ICGOOODFIND

The Lattice Semiconductor ISPLSI1016E-125LTN44 is a landmark high-density CPLD that successfully integrated a robust programmable architecture with the revolutionary convenience of in-system programmability. Its balanced blend of logic capacity, high-speed performance (12.5ns pin-to-pin delay), and low-power 3.3V operation cemented its role as a versatile and reliable workhorse for digital design engineers, effectively consolidating numerous discrete logic ICs into a single, reprogrammable chip.

Keywords: High-Density CPLD, In-System Programmability (ISP), Generic Logic Block (GLB), Global Routing Pool (GRP), E²CMOS Technology.