Muxed pin of Analog To Digital Converter,ADS8548 - Interface Issue
Yes, you would need to use the Configuration Register to activate the internal reference. You would need to perform two 16-bit writes to the device using your parallel bus.

\$\overline{HW}/SW = 1\$ (tied high)

\$\overline{PAR}/SER = 0\$ (tied low)



First

\$\overline{CS} = 0\$

\$\overline{WR} = 0\$

\$DB[15:0] = ??????????????XX\$



then

\$\overline{CS} = 0\$

\$\overline{WR} = 1\$

\$DB[15:0] = XXXXXXXXXXXXXXXX\$



then

\$\overline{CS} = 0\$

\$\overline{WR} = 0\$

\$DB[15:0] = 10?XXX??????????\$



Where X is a don't care and ? means you will need to decide what is correct based on your application.

From the datasheet:



See "Software Mode" on Page 29 and "Configuration (CONFIG) Register" on Page 31 for more information.