When the boundary scan is not used, what will be the pin conditions for the JTAG test access pins?
A13. For the boundary scan, each device uses five pins. These are the JTCLK, JTDI, JTMS, JTRST, and JTDO pins. When the boundary scan is not used, these pins must have a steady value. For JTCLK, it should be pulled high. JTDI and JTMS should be unconnected or high, because they both have an internal 10kΩ pullup resistor. JTRST also has a 10kΩ pullup resistor, and it asynchronously resets the test access port when the pin is toggled from low to high. It needs to be held high or low when the boundary scan is not used. JTDO should be left unconnected.