In-system programming

6- and 10-pin AVR ISP headers

In-system programming (ISP), or also called in-circuit serial programming (ICSP), is the ability of a programmable logic device, microcontroller, chipset, or other embedded device to be programmed while installed in a complete system, rather than requiring the chip to be programmed before installing. It also allows firmware updates to be delivered to the on-chip memory of microcontrollers and related processors without requiring specialist programming circuitry on the circuit board, and simplifies design work.

1. ↑ Oreilly, Designing Embedded Hardware, 2nd Edition by John Catsoulis
2. ↑ "Unified Program and Debug Interface (UPDI) High-Voltage Activation Information – Developer Help". developerhelp.microchip.com. Archived from the original on October 7, 2024. Retrieved December 17, 2024. Shared UPDI pin. This implementation is generally used on devices with smaller packages. The UPDI pin can be re-configured into a GPIO or /RESET pin. In this case, the UPDI functionality is disabled, and a high-voltage source is required to re-enable it. Examples include tinyAVR 0-series, 1-series, and 2-series devices.
3. ↑