FTDI Community
General Category => Discussion - Hardware => Topic started by: Jaholmes on December 02, 2019, 05:31:45 PM
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I'm building a USB sensor application using discrete logic--no MCU or CPU. I have a few candidate designs drawn up, and noticed that I could simplify things if it was permissible to keep WR normally high, then pulse low-high to write. Datasheets for the FT240X and FT245 are a bit ambiguous about this. I should mention that I'm also reading bytes, so RD must also being pulsed low-high periodically. Can this happen while WR is held high--without anything bad happening? Or must WR be low to read? I'd guess it would be ok, but figure I ought to put it out there just in case.
Very best,
Aaron
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Using the UM245R module which carries the FT245.
I hold the read and write lines high by default and only bring RD low to get the necessary -ve edge to make the data available - it must return high for RXF to reset.
I bring write low to clock out the data but the return it high again after at least 50ns.
Seems to work.