XC9500 CPLD Series: Features and Architecture

Posted on Mar 5, 2025 in Computers

Key Features

  • High-Performance Logic:
    • 5 ns pin-to-pin logic delays on all pins.
    • Supports system performance up to 125 MHz.
  • Density Range:
    • Available in a variety of configurations:
    • 36 to 288 macrocells.
    • 800 to 6,400 usable gates, depending on the device size.
  • Programmable Logic Blocks (PLBs):
    • Each internal block is referred to as a Function Block (FB) or Configurable Function Block (CFB).
    • Each block consists of:
      • 36 inputs.
      • 18 macrocells that can implement combinational or sequential logic.
  • FastCONNECT Switch Matrix:
    • Provides programmable interconnects between Function Blocks (FBs).
    • Ensures uniform delay for signal routing and enhances connectivity.
  • I/O Capability:
    • Offers 3.3 V or 5 V I/O compatibility.
    • High-drive 24 mA outputs for robust signal interfacing.
    • Slew rate control on individual outputs to manage signal integrity.
  • In-System Programmability (ISP):
    • Based on Advanced CMOS 5V Fast FLASH technology.
    • Supports 5V in-system programming.
    • High endurance with 10,000 program/erase cycles.
    • Can program/erase over the full commercial voltage and temperature range.
  • Enhanced Design Flexibility:
    • Global and product term clocks for precise timing control.
    • Set and reset signals at both local and global levels.
    • Output enable controls for better output management.
  • Power Efficiency:
    • Includes programmable power reduction mode for each macrocell.
    • Minimizes power consumption in low-activity designs.
  • Extensive Design Security:
    • Pattern security features to protect intellectual property.
    • Safeguards against unauthorized access to design data.
  • Boundary-Scan Support (JTAG):
    • Full compliance with IEEE Std 1149.1 (JTAG) for testing and debugging.

Architectural Advantages

  • Uniform Architecture:
    • Each macrocell and FB is designed with a uniform architecture, enabling predictable timing and consistent performance.
  • High Fan-In Capability:
    • The FastCONNECT switch matrix provides additional logic capability by enabling wired-AND outputs and increasing fan-in without additional timing delay.
  • Flexibility in Logic Design:
    • Each macrocell supports a wide range of configurations:
      • Combinational or sequential functions.
      • Multiple types of flip-flops (e.g., D-type, T-type).
      • Direct or inverted outputs.

Applications

The XC9500 series is ideal for:

  • High-speed state machines.
  • Glue logic for interfacing between systems.
  • Embedded controllers and peripheral devices.


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Structure of a Function Block

Each Function Block consists of the following key components:

  1. Inputs
    • Each FB can receive 36 input signals.
    • These signals are processed as both true and complemented (inverted) forms, resulting in 72 signals for the AND-array.
  2. Programmable AND-Array
    • The AND-array generates product terms based on the logic equations.
    • It can create up to 90 product terms, which are used as inputs to macrocells or control signals (e.g., clock, set/reset, output enable).
    • The AND-array is highly configurable, enabling complex logic functions.
  3. Macrocells
    • Each Function Block has 18 macrocells.
    • A macrocell can implement:
      • Combinational logic (e.g., AND, OR, XOR operations).
      • Sequential logic (using flip-flops like D-type or T-type).
    • Each macrocell can use up to 5 product terms directly from the AND-array.
  4. Local Feedback Paths
    • Outputs from the macrocells can feed back into the AND-array within the same Function Block.
    • This allows local connections, enabling:
      • Creation of fast state machines.
      • Implementation of counters and other feedback-dependent circuits.
  5. Product Term Allocator
    • This mechanism assigns the 90 available product terms to different macrocells.
    • The allocator ensures optimal use of resources and avoids wastage.
  6. Global Signals
    • The Function Block receives global signals, including:
      • Global Clock: Synchronizes operations.
      • Global Reset/Set: Sets or resets all flip-flops in the block.
      • Global Output Enable: Controls whether the outputs are active.
  7. Output Signals
    • The FB generates 18 output signals, corresponding to the 18 macrocells.
    • These outputs are routed through the FastCONNECT matrix for further use or sent directly to the I/O pins.

Key Features of the Function Block

  • Flexible Logic Implementation:
    • Can handle combinational and sequential logic simultaneously.
    • Each macrocell can be configured individually.
  • Efficient Use of Resources:
    • Product terms are dynamically allocated to minimize wastage.
  • High-Speed Operations:
    • Local feedback paths allow quick signal processing without routing outside the FB.
  • Configurable Macrocells:
    • Each macrocell can act as:
      • A logic gate (for simple logic operations).
      • A flip-flop (for storing data).

A macrocell is the basic building block inside a Function Block (FB) in the Xilinx XC9500 CPLD.

Structure of a Macrocell

A macrocell in the XC9500 family has the following key components:

  1. Logic Function Generator
    • The macrocell receives product terms from the AND-array in the Function Block.
    • It can process up to five product terms directly.
    • These product terms are used for:
      • Logic operations (e.g., AND, OR, XOR).
      • Control signals like clock, set/reset, and output enable.
  2. Configurable Flip-Flop
    • Each macrocell includes a register (flip-flop) for sequential logic.
    • Types of flip-flops:
      • D-type flip-flop: Stores a single bit of data.
      • T-type flip-flop: Used in toggle operations (e.g., counters).
    • The flip-flop can be bypassed for purely combinational operations.
  3. Asynchronous and Synchronous Control
    • Each macrocell supports:
      • Asynchronous set/reset: Quickly initializes or clears the flip-flop without waiting for a clock signal.
      • Synchronous set/reset: Controlled by the clock signal for predictable timing.
  4. Output Configurations
    • A macrocell’s output can be:
      • Combinational: Logic operation results are sent directly to the output.
      • Registered: Data is stored in the flip-flop before being sent out.
    • The output can be inverted if required.
  5. Product Term Allocator
    • Allocates the product terms from the AND-array to macrocells efficiently.
    • This flexibility allows sharing product terms among macrocells, minimizing resource usage.


Working of a Macrocell

  • Input Stage:
    • Receives up to five product terms from the AND-array.
  • Logic Processing:
    • Processes these terms using combinational logic (AND, OR, XOR, etc.).
    • Alternatively, stores the output in the flip-flop for sequential logic.
  • Output Stage:
    • The processed signal is sent out either directly (combinational) or through the flip-flop (registered).