How many connections are required for JTAG
From MKRD.info Wiki
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)
VDD
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.