JTAG - Joint Test Action Group

JTAG is a standardised interface for debugging integrated circuits which you can use to debug your Raspberry Pi.

There are two separate JTAG interfaces available on the Pi:

• Alt5 on GPIOs 4, 5, 6, 12 and 13
• Alt4 on GPIOs 22, 23, 24, 25, 26 and 27