ARM, RISC-V контроллеры

А в более новом даташите на LPC210x: 20.8.2 JTAG pin selection The Primary JTAG port can be selected for debugging only when DBGSEL and RTCK pins are HIGH at reset (see Figure 66). If at least one of the DBGSEL or RTCK lines is LOW at reset, JTAG will not be enabled and can not be used for later debugging. Так что в случае LPC210x RTCK не следует подтягивать к земле.