AMD XC18V256VQ44C

Overview

XC18V256VQ44C from Xilinx is a 256-Kbit in-system programmable 3.3V configuration PROM designed to store and serially/parallel load bitstreams into Xilinx FPGAs. It supports Master Serial, Slave Serial, Master-SelectMAP, and Slave-Parallel modes; offers 20,000 program/erase cycles; features IEEE 1149.1 JTAG boundary-scan; and uses a 44-pin VQFP package with 5V-tolerant I/Os.

For engineers reviewing the XC18V256VQ44C datasheet, pinout, applications, or equivalent options, key selection criteria include configuration mode flexibility (serial up to 33 MHz / parallel up to 264 Mb/s), JTAG-initiated FPGA reset via CF pin, cascading support via CEO/CE chaining, and compatibility with Spartan-II, Virtex, and Virtex-II families.

Technical Context

The XC18V256VQ44C implements a flash-based nonvolatile memory architecture with dual configuration interfaces: serial (D0 only) and parallel (D0–D7), selectable via JTAG-accessible control register. Its address counter advances on each rising CLK edge when CE=Low and OE/RESET=High, enabling deterministic timing-critical FPGA boot sequences.

JTAG compliance includes full IEEE 1149.1 support plus XC18V00-specific CONFIG instruction (11101110), which pulses the CF pin low for 300–500 ns to reset and initiate FPGA configuration without power cycling. Boundary-scan registers monitor all I/O pins, and IDCODE 05022093h uniquely identifies this 256-Kbit variant.

Key Specifications

Pinout & Package

XC18V256VQ44C is housed in a 44-pin Very Thin Quad Flat Package (VQFP) with 0.8 mm pitch, RoHS-compliant lead-free finish, and thermal pad not electrically connected. Package dimensions: 10 mm × 10 mm × 1.2 mm (max).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar configuration PROM applications.

Compared with XC18V256PC44C, the XC18V256VQ44C offers superior thermal dissipation and smaller PCB footprint, while XC17V256PC20C sacrifices field-upgradability and testability for lower unit cost and simpler layout - making XC18V256VQ44C optimal for modern SMT-based, upgradable embedded systems.

Availability

XC18V256VQ44C is available at Aetrix Electronics and suitable for industrial PLCs, aerospace reconfigurable computing, medical imaging controllers, and automotive ADAS platforms requiring stable component supply, long-lifecycle support, and guaranteed obsolescence management.

Supply support for XC18V256VQ44C includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Xilinx, now part of AMD, is a pioneer in programmable logic and FPGA technology, delivering high-performance adaptive computing solutions for aerospace, industrial, and communications markets.

The XC18V00 series was engineered specifically to provide secure, in-system programmable configuration storage for Xilinx FPGAs - addressing needs for field-upgradable, JTAG-integrated, and cascaded bitstream loading in mission-critical systems.

FAQ

What configuration modes does the XC18V256VQ44C support?

The XC18V256VQ44C supports serial (Master/Slave) and parallel (Slave-Parallel/SelectMAP) configuration modes, selectable via JTAG-accessible control register. Serial mode uses D0 only and operates up to 33 MHz; parallel mode uses D0–D7 and achieves up to 264 Mb/s at 33 MHz. Default is serial mode.

How does the CF pin function on the XC18V256VQ44C?

The CF pin on the XC18V256VQ44C is controlled exclusively by the JTAG CONFIG instruction (binary 11101110). When executed, it pulses Low for 300–500 ns to drive the connected FPGA's PROGRAM pin, triggering a full configuration reload. This enables remote, in-system FPGA reset without power cycling - a core feature of the XC18V256VQ44C.

Can multiple XC18V256VQ44C devices be cascaded, and how?

Yes, XC18V256VQ44C devices can be cascaded using CEO-to-CE daisy chaining. When the first PROM reaches its terminal count, CEO goes Low to enable the second PROM's CE input. CLK and DATA lines are shared across the chain. This allows storage of larger bitstreams (e.g., for Virtex-II Pro) without external logic - a defined capability of the XC18V256VQ44C family.

What is the endurance and data retention specification for the XC18V256VQ44C?

The XC18V256VQ44C guarantees 20,000 program/erase cycles and minimum 20 years of data retention under specified operating conditions. These values are measured and warranted across the commercial and industrial temperature ranges, and apply directly to the XC18V256VQ44C device as published in DS026 (v3.9).

Is the XC18V256VQ44C compatible with Virtex-II FPGAs?

Yes, the XC18V256VQ44C is explicitly listed in Table 2 of DS026 as compatible with Virtex-II FPGAs including XC2V40 through XC2V8000. It supports Master-SelectMAP and Slave-Parallel modes required by Virtex-II, and its 256-Kbit capacity configures smaller members like XC2V40 (360,096 bits requires XC18V512, so XC18V256 serves as part of multi-PROM solutions).