FPIOA GPIO multiplexer io array
| ch_sel | Channel select from 256 input |
| ds | Driving selector |
| oe_en | Static output enable, will AND with OE_INV |
| oe_inv | Invert output enable |
| do_sel | Data output select: 0 for DO, 1 for OE |
| do_inv | Invert the result of data output select (DO_SEL) |
| pu | Pull up enable. 0 for nothing, 1 for pull up |
| pd | Pull down enable. 0 for nothing, 1 for pull down |
| sl | Slew rate control enable |
| ie_en | Static input enable, will AND with IE_INV |
| ie_inv | Invert input enable |
| di_inv | Invert Data input |
| st | Schmitt trigger |
| pad_di | Read current IO’s data input |