AMD XC18V256SO20I

Overview

XC18V256SO20I from Xilinx is a 262,144-bit (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; features 5V-tolerant I/Os; offers 20,000 program/erase cycles; and operates across industrial temperature range (–40°C to +85°C). It is used in FPGA-based embedded control, communications infrastructure, and reconfigurable computing systems.

For engineers reviewing the XC18V256SO20I datasheet, pinout, applications, or equivalent options, key selection criteria include its 20-pin SOIC package compatibility with Spartan-II/Spartan-IIE and Virtex families, JTAG-initiated CONFIG capability via CF pin, dual-mode configuration flexibility (serial up to 33 MHz / parallel up to 264 Mb/s), and industrial-grade reliability with 20-year data retention.

Technical Context

The XC18V256SO20I implements a flash-based nonvolatile memory architecture with integrated JTAG TAP controller compliant to IEEE Std 1149.1. Its internal address counter advances on each rising CLK edge when CE = Low and OE/RESET = High, enabling deterministic sequential readout synchronized to FPGA CCLK.

It supports cascading via CEO-to-CE daisy-chaining for multi-PROM configurations and provides dedicated boundary-scan instructions including CONFIG (11101110b) to pulse CF low and trigger FPGA reconfiguration without power cycle. The device uses an advanced CMOS FLASH process with 3.3V core (VCC) and selectable 3.3V/2.5V output drivers (VCCO).

Key Specifications

Pinout & Package

XC18V256SO20I is housed in a 20-pin Small Outline Integrated Circuit (SOIC) package with 0.300-inch body width and standard JEDEC MS-013 footprint. Pin 1 is marked by a notch or dot; pins are numbered counterclockwise from top-left corner.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC18V256PC20I, the XC18V256SO20I offers superior thermal dissipation and board-space efficiency for volume production; compared with XC18V512SO20I, it provides optimal cost/performance balance for Spartan-II/XC2S15-class FPGAs without over-provisioning memory.

Availability

XC18V256SO20I is available at Aetrix Electronics and suitable for industrial motor control, telecom baseband processing, reconfigurable test equipment, and avionics signal processing requiring stable component supply across extended product lifecycles.

Supply support for XC18V256SO20I 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, configurable silicon solutions since 1984.

The XC18V00 series was designed specifically to provide robust, in-system programmable configuration memory for Xilinx FPGAs - emphasizing reliability, JTAG integration, and seamless interoperability with Spartan and Virtex families.

FAQ

What configuration modes does the XC18V256SO20I support?

The XC18V256SO20I supports Master Serial, Slave Serial, Master-SelectMAP, and Slave-Parallel modes. Serial mode uses D0 only and runs up to 33 MHz; parallel mode uses D0–D7 and achieves up to 264 Mb/s at 33 MHz. Mode selection is controlled via JTAG-accessible user bits set in Xilinx iMPACT software - the default is serial mode.

How is FPGA configuration initiated using the XC18V256SO20I?

FPGA configuration can be initiated automatically on power-up via the FPGA's mode pins, or manually using the JTAG CONFIG instruction. When executed, CONFIG pulses the CF pin low for 300–500 ns - this signal must be connected to the FPGA's PROGRAM pin. For the XC18V256SO20I (20-pin SOIC), CF is routed to pin 7 via the CF→D4 programming option when parallel mode is disabled.

Does the XC18V256SO20I support cascading with other PROMs?

Yes, the XC18V256SO20I supports daisy-chain cascading using the CEO (Chip Enable Output) pin. When the internal address counter reaches terminal count, CEO goes low and enables the CE input of the next PROM in the chain. All CLK and DATA lines are shared across the chain, allowing concatenated bitstreams for larger FPGAs like XC2V1000 or multi-FPGA systems.

What is the purpose of the VCCO pin on the XC18V256SO20I?

The VCCO pin supplies voltage to the XC18V256SO20I's output drivers and sets the logic-high level of D0–D7 and CEO outputs. It accepts either 3.3V or 2.5V, allowing direct interface with FPGA I/O banks operating at either voltage. VCCO must be decoupled independently from VCC, and its voltage must match the target FPGA's configuration I/O standard to prevent signal integrity issues.

Is the XC18V256SO20I compatible with modern Xilinx FPGA families?

The XC18V256SO20I is fully compatible with Spartan-II, Spartan-IIE, Virtex, Virtex-E, and early Virtex-II FPGAs - as confirmed in Xilinx DS026 Table 2. While newer 7-series and UltraScale FPGAs use different configuration schemes (e.g., QSPI flash), the XC18V256SO20I remains the certified solution for legacy and long-lifecycle industrial designs based on those supported families.