we are currently observing an unexpected behavior in our AD2S1210 software driver. The RDC chip is currently accessed from an ADSP-BF537EZ-KIT LITE Evaluation Board via SPI. Reading the configuration registers – both after reset and after writing – always returns the MSB (D7) as set (‘1’). This behaviour differs from what we expect from the specification (AD2S1210, Rev. A, D07467-0-2/10(A), section „Address/Data Bit“). This is not really a problem in case of the configuration registers, but the same effect can be observed with the data registers
in configuration mode. Thus, the full range of the register values cannot be used.
Even worse, also in „Normal Mode“, i.e. with A0=0, reading the 16-bit data words (Position/Velocity) returns the MSB (D15) always as set.
Most probably, the SPI communication can be ruled out as the cause, since the read values have been verified with measured SPI signal levels.
Furthermore, a „stuck-at-1 fault“ in the specific chip can be ruled out, because the first read access after issuing a soft reset returns 0, provided a certain delay is not observed.
This effect, i.e. a notable delay after a soft reset before valid register values can be read, is not mentioned in the specification either.
Can anyone please give any hints what we might do wrong in accessing the RDC configuration interface? Is there any software driver or example code (preferably in C) available?
in advance for your help!