I am working on an interface to configure ADRF6755 on its I2C bus, and for that I use a FPGA from Altera (Cyclone IV EP4CE22) to generate the SDA and SCLK signals to the ADRF (to its pin 29 and 30). I followed the configuration sequence pointed out in page 35 as recommended on the device datasheet. Everything has worked out to several registers, and I got the acknowledge bit back without a problem, which for me means that the I2C interface is OK from a hardware point-of-view. But when I send the command to write the register CR27 (0x1B) using the I2C, the FPGA doesn’t receive back the acknowledge bit. I would like to know if there is anything that I have to do before I try to set this register, since I do that after following the recommended sequence, which, up to the point of writing to CR27, has been OK.