How many connections are required for JTAG

The JTAG interface standard requires the following connections:

• TDI (Test Data In)
• TDO (Test Data Out)
• TCK (Test Clock)
• TMS (Test Mode Select)

However, when designing your hobby project with a JTAG interface, allocate at least 8 pins on a header (dedicated header is best), for the following signals:

• TDI
• TDO
• TCK
• TMS
• TRST (Test Reset)
• V_DD
• GND
• DONE

Plus any chip-specific or platform-specific configuration pins. For example, most devices and programmers use the DONE signal to specify that the programming succeeded.