Efficient Logic and Memory Implementation with FLEX 10K EABs

The Altera FLEX 10K family of programmable logic devices (PLDs) offers a unique and powerful combination of logic and memory resources, making it highly suitable for a wide range of applications. One of the key features of the FLEX 10K architecture is the Embedded Array Block (EAB), which provides a flexible and efficient way to implement complex custom functions, including memory, logic, and even specialized functions like Fast Fourier Transforms (FFTs) and Finite Impulse Response (FIR) filters.
EAB Architecture
Each FLEX 10K EAB contains 2,048 bits of RAM, which can be configured in various ways to meet different design requirements. The EABs can be used to create synchronous RAM, ROM, dual-port RAM, FIFOs, and other memory types. The data bus width can range from 1 to 8 bits, and the address bus width can go up to 11 bits. This flexibility allows designers to optimize their memory usage based on the specific needs of their application.
One of the significant advantages of EABs is their predictable and easy-to-use timing. Unlike distributed RAM in some FPGAs, EABs ensure consistent access times, making them ideal for high-performance applications. Additionally, EABs contain input, output, and address registers that can be used to synchronize a design, further enhancing performance and reliability.
Using EABs for Memory Implementation
The FLEX 10K EABs can be configured in various sizes to create different memory configurations. For example, an EAB can be set up as a 256x8 RAM block, a 512x4 RAM block, a 1024x2 RAM block, or a 2048x1 RAM block. To achieve larger memory blocks, multiple EABs can be cascaded or multiplexed. The MAX+PLUS II software, provided by Altera, automatically handles the cascading of EABs, ensuring that the access time remains consistent regardless of whether the EABs are cascaded or not.
Cascading EABs allows designers to create wider RAM blocks without the need for additional logic, thus maintaining the same access time as non-cascaded EABs. For instance, two 256x8 RAM blocks can be combined to form a 256x16 RAM block, or two 512x4 RAM blocks can be combined to form a 512x8 RAM block. This flexibility in memory configuration is crucial for applications that require large amounts of memory but are constrained by space or speed requirements.
Software Support and Design Tools
Designers can leverage various tools and methodologies to implement memory functions using FLEX 10K EABs. The MAX+PLUS II development system supports the Library of Parameterized Modules (LPM) standard, which allows designers to specify memory parameters such as width and address width. This feature enables the creation of custom memory configurations that can be efficiently synthesized into the FLEX 10K architecture.
In addition to MAX+PLUS II, designers can use standard Electronic Design Automation (EDA) tools from vendors like Mentor Graphics, Intergraph, Viewlogic, and Cadence. These tools, in conjunction with the LPM standard, provide a powerful environment for creating and optimizing memory designs. For example, designers can use VHDL to declare LPM entities with generics that allow parameters to be passed down from upper-level files. This approach ensures that the memory design is both flexible and efficient.
Applications and Performance
The FLEX 10K EABs are particularly well-suited for applications that require high-speed memory and efficient logic implementation. One such application is the implementation of FFT algorithms, which are widely used in signal processing for tasks such as signal analysis, radar processing, and communications. The FLEX 10K architecture, with its embedded array and logic array, provides the necessary performance and flexibility to implement FFTs efficiently.
For example, FFTs with lengths ranging from 256 to 512 points can be implemented using on-board memory resources, such as EABs. This capability significantly reduces the need for external memory, thereby conserving I/O pins and PCB space. The performance of these FFT implementations is also impressive, with transform times ranging from 94 microseconds to 190 microseconds for different data and twiddle precisions.
Conclusion
The Altera FLEX 10K family, with its Embedded Array Blocks, offers a highly efficient and flexible solution for implementing complex logic and memory functions. The EABs provide a predictable and easy-to-use timing model, making them ideal for high-performance applications. With the support of powerful design tools and methodologies, designers can create custom memory configurations that meet the specific requirements of their applications. Whether it's implementing FFTs, FIR filters, or other memory-intensive functions, the FLEX 10K EABs provide a robust and efficient platform for achieving optimal performance and functionality.
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