C code for analog read of SD24 ADC (MSP430I2041)
You forgot to configure the reference voltage (the default is an external reference, which you did not mention).

Section 13.2.7.2 of the User's Guide says:


  When SD24LSBTOG = 1, the SD24LSBACC bit is automatically toggled each time the corresponding
  channel's SD24MEMx register is read. This allows the complete digital filter output result to be read with
  two read accesses of SD24MEMx.