Prepared by: Technical Analysis Unit Disclaimer: Information provided for educational and repair purposes only. Icom Inc. does not endorse this report.
| Error | Likely Cause | Solution | |-------|--------------|----------| | | Wrong COM port or cable | Verify port in Device Manager; use native RS-232 | | Model Mismatch | Wrong firmware region | Try IC-F21S setting or different software version | | Checksum Error | Corrupt codeplug | Read radio twice, compare hex dump | | No Response | Radio not powered or clone cable | Measure voltage at Molex pin 1 (GND) and pin 2 (5V) | icom ic-f21 programming software
Note: Icom no longer sells or supports CS-F21 directly. It is considered abandonware for legacy products. icom ic-f21 programming software