0 Replies Latest reply on Jan 6, 2016 3:37 AM by MichelleC_Intel

    Intel® Quark™ Microcontroller D2000 - Recover JTAG access after muxing JTAG pins with another function (e.g. UART_B)



      The D2000's JTAG pins can be muxed with other functions (including UART1, PWMs & GPIO’s). JTAG pins are muxed out by default at POR and once they are assigned to a different function, it is impossible to access the TAP without a reset. 

      e.g. Because UART_B signals are multiplexed with the JTAG signals, by using UART_B, your application disables the JTAG interface. 


      It is essential that the JTAG TAP be accessed before any pin muxing happens and a function is provided to implement a BootROM hook to guarantee enough time for a JTAG access.
      The “pull pin 0 low” feature it stops the application from executing thus allowing JTAG to be used.


      By grounding Pin 0 on the CRB you can access the JTAG Interface (to allow a new ROM / Application to be flashed). Jumpers  J7, J9, J10, J12, and J13 should also be set to their default positions.. shown below.