6176 - MachXO2/MachXO3: Why there is no JTAG external pullups (TDI,TDO,TMS) recommendation in our documents such Hardware Checklist and Programming and Configuration user guide while external pull-ups were added in our Lattice demo and evaluation boards.
MachXO2 and MachXO3L/LF TDI,TDO,TMS signals have internal pull-ups, so external pull-ups are not required. However, good engineering practice for a critical bus like JTAG is to augment the internal pull-ups with external if the bus will not always be driven. On most of our evaluation and demo boards, the JTAG is driven by the FTDI bridge chip, and the JTAG outputs are tri-stated at times.