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.