AMD XC18V256PC20I

Overview

XC18V256PC20I from Xilinx is a 256-Kbit in-system programmable (ISP) configuration PROM designed to store and serially load bitstreams into Xilinx FPGAs in Master Serial mode. It delivers 262,144 bits of Flash-based nonvolatile memory, supports 20,000 program/erase cycles, operates across industrial temperature range (–40°C to +85°C), and features IEEE 1149.1 JTAG boundary-scan for in-system programming and FPGA configuration initiation - used in reconfigurable logic systems for telecom baseband processing.

For engineers reviewing the XC18V256PC20I datasheet, pinout, applications, or equivalent options, key selection criteria include its 20-pin PLCC (PC20) package, dual-configuration support (serial up to 33 MHz), 5V-tolerant I/Os, JTAG CONFIG command capability, and compatibility with Spartan-II, Virtex, and early Virtex-II FPGAs requiring ≤262,144-bit configuration data.

Technical Context

The XC18V256PC20I implements a Flash-based memory array with an internal address counter driven by CCLK in serial mode or external clock in Slave-Parallel/SelectMAP modes. Its JTAG TAP controller supports CONFIG, IDCODE, USERCODE, and boundary-scan instructions, enabling FPGA reset-and-reconfigure via CF pin pulsing without power cycle.

It uses a 3.3V core supply (VCC) and configurable 3.3V/2.5V output drivers (VCCO), with all I/O pins 5V-tolerant. The OE/RESET pin is bidirectional open-drain and non-programmable in polarity; CE assertion places the device in low-power standby with address reset and outputs in high-impedance state.

Key Specifications

Pinout & Package

XC18V256PC20I is housed in a 20-pin plastic leaded chip carrier (PC20) package with 0.6-inch body width, gull-wing leads, and through-hole mounting compatibility. Pin 1 is marked with a notch or dot; pins not listed in Table 1 are no-connects (NC).

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC18V256SO20I, XC18V256PC20I offers superior mechanical stability in vibration-prone systems; compared with XC18V512PC20I, it provides cost-optimized storage for smaller FPGAs while sharing identical footprint and toolchain support.

Availability

XC18V256PC20I is available at Aetrix Electronics and suitable for telecom infrastructure, industrial motor drives, medical imaging subsystems, and aerospace avionics requiring stable component supply over extended product lifecycles.

Supply support for XC18V256PC20I 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 devices, specializing in FPGAs, adaptive SoCs, and associated configuration solutions since 1984.

The XC18V00 series was engineered specifically to provide in-system programmable, Flash-based configuration storage for Xilinx's early FPGA families - prioritizing JTAG accessibility, industrial temperature operation, and seamless integration with Alliance/Foundation design tools.

FAQ

What configuration modes does the XC18V256PC20I support?

The XC18V256PC20I supports serial (Master/Slave) and parallel (Slave-Parallel/SelectMAP) configuration modes. Serial is the default; parallel mode is enabled via JTAG-accessible control register using Xilinx iMPACT software. Mode selection determines whether D0 only (serial) or D0–D7 (parallel) are active outputs.

How does the JTAG CONFIG instruction function on the XC18V256PC20I?

The JTAG CONFIG instruction pulses the CF pin low for 300–500 ns, which must be connected to the FPGA's PROGRAM pin. This triggers a full FPGA reset and initiates configuration reload without power cycling. The XC18V256PC20I itself remains powered and ready - confirmed in DS026 Section "Initiating FPGA Configuration".

Is the XC18V256PC20I pin-compatible with other XC18V00 family members in the PC20 package?

Yes - all XC18V00 variants in the PC20 package (e.g., XC18V01PC20I, XC18V512PC20I) share identical pinout, voltage ratings, and interface behavior. Only memory capacity and terminal count differ; this enables direct substitution where bitstream size permits, as verified in DS026 Table 1 and Figure 15.

What is the role of the OE/RESET pin on the XC18V256PC20I?

The OE/RESET pin is a bidirectional open-drain terminal that drives the FPGA's INIT pin. During power-up, it is held low for ~1 ms until VCC stabilizes, then pulled high to release INIT and begin configuration. Its polarity is fixed and non-programmable - a critical timing signal for synchronous FPGA startup per DS026 Section "Reset Activation".

Can the XC18V256PC20I be used with Virtex-II FPGAs?

No - the XC18V256PC20I is not intended for Virtex-II devices. DS026 Table 2 lists only Virtex, Virtex-E, Spartan-II, and Spartan-IIE FPGAs as compatible. Virtex-II requires larger PROMs (e.g., XC18V04 or cascaded units) due to bitstream sizes exceeding 262,144 bits - confirmed by configuration bit counts in Table 2.