ADS1278 to OMAP3530 via SPI

Hi John,

1.  ADS1278 has no "chip enable/select" line.  We are only using one ADS1278.  How should the "chip select" line on the OMAP3530 be terminated?

Since the "chip select" line from the OMAP3530 is an output from the processor, there is no need to terminate the line, you could simply leave it open or tied it to GND/Vdd through a pull-down/up resistor keeping it accessible for future use.

2.  ADS1278 has a DRDY (not) line which starts the data transfer process.  This is not part of the SPI "standard."  The line goes high and then the ADS1278 expects the SPI SCLK from the SPI Master (OMAP3530).  When it receives the SPI SCLK the data transfer begins on the SPI MISO line.  Should the DRDY (not) line be connected to a digital I/O line on the OMAP3530 and continuously monitored by the OMAP?

You are correct, /DRDY is not part of the "SPI Standard" - for the ADS1278, the /DRDY acts like an interrupt in SPI modes of operation.  While not part of the SPI protocol, this signal would normally be part of an interrupt sub routine that starts the transfer of data between the ADC (the SPI slave) and the host processor (the SPI Master).  The /DRDY signal actually goes low once data is ready to be processed and returns high with the first falling edge of the SPI clock.  Ideally, the /DRDY output would be tied to a dedicated external interrupt (falling edge or low level triggered) rather than a GPIO which would reduce some of the processing overhead associated with continuously monitoring that line via GPIO.

3.  Because the SPI MOSI line is not used, how should it be terminated?

Like the /CS output from the OMAP3530, MOSI would not need to be terminated.  You could again employ a pull-up/down to this output from the processor keeping it accessible for future use.