Serial Communication (IEEE 1149.1 standard) initially developed to test the printed circuit boards, but now become a defacto standard for debugging low level firmware to different operating system applications.
1. TDI (Test Data In)
2. TDO (Test Data Out)
3. TCK (Test Clock)
4. TMS (Test Mode Select)
5. TRST (Test Reset)
IEEE 1149.1 Daisy Chain
IEEE 1149.7 (Reduced Pin Count) Daisy Chain
Supported TCK is 10 – 100 MHZ