What is the ISC file format?
An .isc file is a text-based In-System Configuration (ISC) descriptor produced by the Xilinx ISE Design Suite for FPGA programming over JTAG boundary-scan chains - a method that allows engineers to program or verify an FPGA while it remains installed on a target board.
The file describes JTAG chain topology, device identifiers, and configuration sequences for legacy Xilinx device families including Spartan-3/6 and Virtex-4/5/6. It is a plain ASCII text document, typically beginning with # comment lines or device header keywords, and is consumed by the ISE iMPACT programming tool.
Xilinx ISE Design Suite reached its final release - version 14.7 - in October 2013 and entered sustaining mode with no further development. AMD, which acquired Xilinx in February 2022, still provides ISE 14.7 as a legacy download only. New designs targeting UltraScale+ and Versal families use Vivado Design Suite with .xdc constraint files instead; Vivado has no equivalent .isc file type.
ISE 14.7 continues to run on Windows 10/11 via the legacy installer.
Security & safety
RISK: LOWPlain-text FPGA configuration file; no executable content. No known security risk.
Format details
in a nutshell- Internet Storm Center / ISC BIND zone file - Some firewall/network tools use .isc as a configuration file extension (unrelated to Xilinx).
Programs that open ISC files
Windows2 apps
Xilinx ISE Design Suite 14.7
Free Open ISE Project Navigator; the .isc file is used internally by iMPACT programmer tool. 
Linux1 app
Technical details
deep spec| Format type | Text-based FPGA JTAG In-System Configuration descriptor |
| Encoding | ASCII plain text |
| Typical size | 1 KB - 50 KB |
| Produced by | Xilinx ISE Design Suite iMPACT programmer tool |
| Target device families | Spartan-3/6, Virtex-4/5/6 (legacy Xilinx FPGA families) |
| Configuration method | JTAG boundary-scan chain - programs or verifies FPGA while installed on target board |
| Final tool version | Xilinx ISE 14.7 (October 2013); sustaining mode only, no further development |
| Current owner | AMD (acquired Xilinx in February 2022); ISE 14.7 maintained as legacy-only download |
| Successor toolchain | Vivado Design Suite with .xdc constraint files (no .isc equivalent in Vivado) |
| OS support | Windows (including 10/11 via legacy installer), Linux (RHEL/CentOS) |
| Magic bytes | None; file typically begins with # comment lines or device header keywords |
| Released | circa 2000 (Xilinx ISE Design Suite first released early 2000s) |
| Latest version | ISE 14.7 (October 2013 - final release; sustaining mode only) |
| Specification | docs.amd.com |
ISC conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about ISC files.
