Programming and Applications of the Microchip ATF1508AS-7AX100 CPLD

The Microchip ATF1508AS-7AX100 is a high-performance, high-density Complex Programmable Logic Device (CPLD) built on an advanced electrically erasable technology. It represents a flexible and reliable solution for a wide range of digital logic applications, offering a robust alternative to fixed-function integrated circuits. Its architecture is based on macrocells, allowing designers to implement complex combinational and sequential logic with significant efficiency.

Device Architecture and Key Features

At the core of the ATF1508AS are multiple Logic Array Blocks (LABs), each containing 16 macrocells. The specific -7AX100 variant features 128 macrocells, providing ample resources for moderately complex designs. A key strength of this architecture is its deterministic timing model; signal delays are predictable and consistent, which is critical for state machine control and other timing-sensitive applications. The device offers up to 100 user I/O pins (hence the AX100 suffix), enabling interface with a multitude of external components. It supports a wide operating voltage range from 3.0V to 5.5V, making it suitable for both modern low-voltage and legacy 5V systems. The 7ns pin-to-pin logic delay (for the -7 speed grade) ensures high-speed operation, capable of handling clock frequencies well over 100 MHz.

Programming the ATF1508AS

Programming the ATF1508AS is a streamlined process facilitated by industry-standard tools. The typical workflow involves several key steps:

1. Design Entry: The desired logic function is captured using Hardware Description Languages (HDLs) like VHDL or Verilog, or through schematic entry in an Electronic Design Automation (EDA) tool.

2. Synthesis and Fitting: The design is synthesized into a netlist of logic gates and then fitted (placed and routed) onto the CPLD's specific resources (macrocells, I/Os, interconnect).

3. Functional and Timing Simulation: The fitted design is rigorously simulated to verify both its logical correctness and its timing performance within the device.

4. JEDEC File Generation: The verified design is translated into a JEDEC file (JED), which is a standard format containing the programming information for the fuse array within the CPLD.

5. Device Programming: The JED file is transferred to the physical CPLD using a dedicated programmer or via an In-System Programming (ISP) header. The ATF1508AS supports IEEE 1149.1 (JTAG) interface for programming and boundary-scan testing, which is invaluable for debugging and programming boards after assembly.

Primary Applications

The flexibility of the ATF1508AS makes it ideal for numerous applications, including:

Glue Logic Integration: Its most traditional use is to replace numerous discrete "glue logic" ICs (e.g., gates, flip-flops, buffers) on a PCB, thereby reducing board space, component count, and cost.

Address Decoding and Bus Interface: It is perfectly suited for generating complex chip select signals and implementing custom bus arbitration or protocol in microprocessor and microcontroller-based systems.

State Machine Control: The deterministic timing makes it excellent for implementing finite state machines that control system power-up sequences, data flow, or mode switching.

I/O Expansion and Interfacing: It can be used to manage and expand the I/O capabilities of a microcontroller, interfacing with buttons, LEDs, displays, and other peripherals.

Protocol Bridging: The device can act as a bridge between different communication protocols (e.g., between SPI and a parallel interface), translating timing and data formats.

ICGOODFIND: The Microchip ATF1508AS-7AX100 CPLD remains a highly capable and versatile logic integration solution. Its high macrocell count, predictable timing, and 5V tolerance on many I/O pins make it particularly valuable for industrial control, telecommunications, and automotive systems where reliability and real-time performance are paramount. The mature JTAG-based programming ecosystem ensures a smooth and reliable development process from design to deployed product.

Keywords:

1. CPLD

2. JTAG Programming

3. Macrocell

4. Deterministic Timing

5. Glue Logic