More info:
START is tied low.
RESET is tied HIGH.
CLKSEL is tied HIGH (internal clock).
CS is tied LOW (ads1298 is the only part on the SPI bus).
Is CS actually the problem? We could be getting an extra clock, misaligning the commands.
The lines we have connected to the microprocessor: DRDY, DIN, DOUT, SCLK, PWDN.
Can we use PWDN to reset the serial interface if we don't have CS?