Issue link: https://iconnect007.uberflip.com/i/304995
54 SMT Magazine • May 2014 provide a good ground connection between the JTAG Controller and the board to improve the signal quality. 2. Use twisted or parallel pairs, each con- taining one signal and a ground, for each TAP signal. This is most important for the clock sig- nal (TCK) but also any other signals that are and significantly, improved by making the fol- lowing changes, as shown in Figure 3: 1. Add at least one ground test pin as close as possible to the TAP signal test pins in the test fixture. This isn't for the main ground connec- tion used to power the board, but instead is to feATuRe SIGNaL INTEGRITy IN TEST FIXTURES continues figure 2: A bad test fixture design, due to large loop areas for all TAP signal connections. figure 3: A good test fixture design, keeping the loop area small for all TAP signal connections.