XC18V256SO20I

Overview

The XC18V256SO20I is a 3.3V in-system programmable configuration PROM from the XC18V00 series, manufactured by Xilinx (now AMD). It provides 256 Kbit (262,144 bits) of non-volatile storage for FPGA bitstreams. The device supports serial and parallel configuration modes with up to 33 MHz clock speeds. It features 5V tolerant I/Os, IEEE 1149.1 JTAG support, and an endurance of 20,000 program/erase cycles. The component is housed in a 20-pin SOIC package.

Feature Summary

• In-system programmable via standard 4-pin JTAG protocol
• Supports Master Serial, Slave Serial, and SelectMAP configuration modes
• 5V tolerant I/O pins compatible with mixed voltage systems
• Cascadable architecture using Chip Enable Output

Applications

• Configuration of Xilinx Virtex-II and Spartan-II FPGAs
• Storage of FPGA configuration bitstreams in embedded systems
• In-system programming for design iteration and field updates

Procurement Notes

Verify the package suffix 'SO' corresponds to the 20-pin Small Outline Integrated Circuit (SOIC) form factor required for your PCB layout. Confirm the temperature grade 'I' indicates industrial range operation if applicable to your environment. Ensure the manufacturer designation aligns with current AMD/Xilinx product lines as ownership has transferred. Cross-reference the specific IDCODE for verification during JTAG programming.

Selection Notes

Select this component when a 256 Kbit capacity is sufficient for the target FPGA configuration data. The 20-pin SOIC package is suitable for space-constrained designs requiring surface-mount technology. Consider cascading multiple devices if the bitstream exceeds 256 Kbits. Verify that the target FPGA supports the desired configuration mode, such as Master Serial or Slave Parallel, to ensure proper interface compatibility.

Part Context

This part belongs to the XC18V00 series of reprogrammable PROMs designed specifically for configuring Xilinx FPGAs. It replaces older one-time programmable (OTP) solutions like the XC17V00 series, offering the advantage of in-system reprogramming. The series includes various densities ranging from 256 Kbit to 4 Mbit, allowing designers to match memory size precisely to FPGA requirements.

Replacement Considerations

XC18V256VQG44C

FAQ

How is the configuration mode selected?

The configuration mode is selectable through a user control register accessible via JTAG, typically set using Xilinx iMPACT software. Serial output is the default mode.

What is the function of the CF pin in 20-pin packages?

The 20-pin packages do not have a dedicated CF pin. The CF function can be routed to pin 7 using the CF --> D4 setting, provided parallel output mode is not used.

Can this device be daisy-chained with other PROMs?

Yes, multiple XC18V00 devices can be concatenated by connecting the CEO output of one device to the CE input of the next, allowing for larger configuration memories.