Lattice Semiconductor ISPLSI1016-90LT44: A Comprehensive Technical Overview of the High-Density Programmable Logic Device
The Lattice Semiconductor ISPLSI1016-90LT44 stands as a quintessential representation of high-density programmable logic from a pivotal era in digital design. As a member of the renowned high-density ispLSI 1000E family, this device integrated complex logic functions into a single, reprogrammable chip, offering a powerful alternative to large collections of fixed-function TTL components. Its architecture and in-system programmability (ISP) made it a popular choice for a wide range of applications, from telecommunications and networking to industrial control and computer peripherals.
Fabricated on an advanced E²CMOS technology, the core of the ISPLSI1016-90LT44 is its Generic Logic Block (GLB) structure. The device contains 16 GLBs, each capable of performing a wide variety of combinatorial and sequential logic operations. These blocks are interconnected by a highly versatile Global Routing Pool (GRP), a central switch matrix that ensures efficient and predictable signal routing across the entire device. This global interconnect scheme provides 100% routability, a critical feature that simplifies the design process and maximizes the utilization of available logic resources.
A key specification highlighted in its part number is its speed grade. The suffix `-90` denotes a maximum pin-to-pin delay of 7.5ns, enabling high-performance operation with system clock frequencies well above 50 MHz. This made it suitable for implementing high-speed state machines, address decoders, and complex interface logic. The `LT44` suffix specifies a 44-pin Thin Quad Flat Pack (TQFP) package, a surface-mount form factor that was ideal for space-constrained PCB designs.
The most revolutionary feature of the ispLSI family is its In-System Programmability (ISP). Unlike earlier PLDs that required physical removal from a circuit board for erasing and reprogramming, the ISPLSI1016 could be reconfigured in-situ via a standard 5-wire JTAG (IEEE 1149.1) interface. This capability dramatically accelerated development cycles, facilitated field upgrades, and enabled rapid design iterations and debugging without hardware changes.
The device is organized into two macrocell-rich banks of I/O pins, which are connected to the GRP through an Output Routing Pool (ORP). This structure provides flexible output configurations, including registered or combinatorial outputs with programmable tri-state control. The I/O pins are compliant with 3.3V and 5V voltage standards, enhancing its interoperability in mixed-voltage systems.
ICGOOODFIND: The Lattice Semiconductor ISPLSI1016-90LT44 is a historically significant high-density CPLD that empowered designers to integrate complex digital systems. Its robust architecture, featuring a global routing pool and generic logic blocks, combined with the groundbreaking convenience of in-system programmability, established a strong legacy in logic design. It remains a classic example of the transition from simple PLDs to more complex, user-configured logic devices that paved the way for modern FPGAs.
Keywords: High-Density Programmable Logic, In-System Programmability (ISP), Generic Logic Block (GLB), Global Routing Pool (GRP), E²CMOS Technology
