JTAG: The connector pins are: 1. TDI (Test Data In); 2. TDO (Test Data Out); 3. TCK (Test Clock); 4. TMS (Test Mode Select); 5. TRST (Test Reset) optional. Source Wikipedia
JTAG (named after the Joint Test Action Group which codified it) is an industry standard for verifying designs and testing printed circuit boards after manufacture. Source Wikipedia
