Hello,
I am bringing up a board with an STM32 processor controlling a TRF7970A in parallel mode. From looking at the EVM, it looks like the chip is in parallel mode by default, so I am applying power, then waiting at least 5ms, then bringing EN2 up, then bringing EN1 up (within 1ms). I then send SOFT_INIT followed by IDLE direct commands. I write 0x21 to MODULATOR_CONTROL register, then attempt to read the MODULATOR_CONTROL register back and the chip does not respond. The whole sequence can be found here: http://i.imgur.com/Yg2iKOn.png. The top trace is the clock output coming from TRF7970A, the green trace is EN1 and blue trace is EN2. D8 is CLK and D0..7 are DATA0..7. I tried to draw an arrow pointing to the second to last clock pulse (the one before stop condition) during which I was expecting to get data from the chip, but it is silent. I stepped through this code and was able to measure that the data pins are in high impedance mode during that clock, so it looks like the TRF chip is not driving them.
Can you anyone provide pointers as to any issues that they are seeing or a review of the pin activation sequence that I should be looking for? Finally, should I expect that the chip is set to parallel mode by default or do I have to do something during bootup to put it in parallel mode? Thanks!
