JTAG

Joint Test Action Group (JTAG) is the common name for an industry standard access port. It is commonly used for IC level debugging. The interface is a special four/five pin interface added to a chip, to enable multiple chips to be chained together, needing only one data probe to test.

Hooking it up

 * 1) TDI (Test Data In)
 * 2) TDO (Test Data Out)
 * 3) TCK (Test Clock)
 * 4) TMS (Test Mode Select)
 * 5) TRST (Test Reset) optional.