I am sending I2C commands to a UCD9240 from an FPGA on the Xilinx SP605 board. I can send CLEAR_FAULTS and PAGE commands OK but when I send FREQUENCY_SWITCH the response is NACK even if I request the default frequency of 500 kHz. I have a sensitive ADC attached to the FMC and I wish to implement a spread spectrum EMI reduction scheme to constantly sweep the frequency up and down by a few kHz. I have tried preceding the FREQUENCY_SWITCH with PAGE 0x00 and PAGE 0xFF. Every I2C command is bracketed with START and STOP. I have tried varying the I2C clock. The I2C driver supports clock stretch.
Thanks in advance,
Andrew.