TI ADS7250 Read From SPI and SPI1 Simultaneously
You can't use the normal SPI library for communicating with this device properly. Well, you can, but you will only be able to use one channel - the other will be completely ignored.
SPI only works on one MISO pin - you need two.  There are two other types of &quot;SPI&quot; that are used by devices, most notably SPI flash chips: DSPI and QSPI (dual SPI and quad SPI). You want DSPI.
Unfortunately the Arduino doesn't do DSPI, so you will have to &quot;bit bang&quot; it, which means manually manipulating the IO pins to create your own SPI signals in software.
Now... on to the datasheet:
The important part is the timing diagram on page 9. From that you can see that you just send 32 clock pulses and the chip responds, after 15 pulses, with the data.
So if you just do 4 8-bit transfers back-to-back then you get the data. It doesn't matter what you &quot;send&quot; in those transfers since the MOSI pin isn't connected to anything.
As far as speed goes, 24MHz is the maximum speed that it will run at. The actual speed is dictated by the Arduino and how fast you manipulate the SCK pin. That can be as slow as 1x10-1000Hz if you really want.
Data should be read on the falling edge of SCK.
So you could write a little routine that looks like:
uint32_t resa = 0;
uint32_t resb = 0;

pinMode(SCK, OUTPUT);
pinMode(SDI_A, INPUT);
pinMode(SDI_B, INPUT);
pinMode(CS, OUTPUT);
digitalWrite (CS, HIGH);


digitalWrite (CS, LOW);
for (int i = 0; i &lt; 32; i++) {
    digitalWrite(SCK, HIGH);
    digitalWrite(SCK, LOW);
    resa &lt;&lt;= 1;
    resb &lt;&lt;= 1;
    resa |= digitalRead(SDI_A);
    resb |= digitalRead(SDI_B);
}
digitalWrite (CS, HIGH);

Serial.print(&quot;A: &quot;); Serial.println(resa);
Serial.print(&quot;B: &quot;); Serial.println(resb);

So for 32 iterations you pulse the clock HIGH then LOW, then shift each result 1 bit to the left, and then add in the newly read bit into the lowest bit position.
You could speed up operation by using direct port manipulation and avoiding the slow digitalWrite() and digitalRead() functions.