3 Replies Latest reply on May 6, 2020 2:34 AM by RaktimR_11

    CYQ954907AEVAL1F JTAG short-circuit


      I need to use Segger J-Link with CYQ954907AEVAL1F, but I am quite concerned, because there looks to be a short-circuit between the JTAG header and the FT2232HQ.
      The FT2232HQ seems to be configured using a EEPROM (AT93C46D). This means as soon as power is applied top the board, the FT2232HQ will activate the FTDI_JTAG_TCK, FTDI_JTAG_TDI, and FTDI_JTAG_TMS pins as outputs.


      If I connect a Segger J-Link, then there will be a short-circuit between the Segger J-Link and the FT2232HQ on pins FTDI_JTAG_TCK, FTDI_JTAG_TDI, and FTDI_JTAG_TMS, as both the FT2232HQ and the J-Link will continously drive these pins as outputs.


      This issue has been reported before, but was never properly understood or answered:

      CYW943907AEVAL1F external JTAG signals driving against FTDI JTAG signals
      The fact that the board is not simultaneously programmed by both J-Link and FT2232HQ is beside the point.
      The pins will short-circuit whether there is any active programming going on or not.