3 Replies Latest reply on Feb 5, 2014 8:53 AM by MichaelF_56

    Are pullup resistors always needed on 20732 SCL and SCA pins?

    ShawnA_01

      The IIC and SPI (aka SPIFFY1) interfaces share Pin 16 (SCL/CLK) and Pin 15 (SDA/MOSI) of the 20732 device.  Page 19 of 20732-DS104-RDS.pdf (dated 9/17/2013) states pullups are required on these open drain I/O pins.

       

       

      Schematics showing the EEPROM based designs consistently remind us that pullup resistors are required on these pins.

       

       

      However, some schematics showing the (SPI) Serial Flash based implementation (e.g. 920732EVAL_Q32_P3-HWUM100-RDS.pdf) do not show pullup resistors.

       

       

      I *assume* the IIC or GPIO interface is the default multiplexer setting for these pins after RESET, in which case there could (?) be a window of opportunity for an input to float before the software has an opportunity to re-configure the mux to use the SPIFFY1 interface instead?

       

       

      Are the resistors mandatory (?), recommended (?), or truly not needed when using a serial flash?