D0, pin 13, an output. Normally in Hi-Z gets enabled when
- Reading the STRB pin (18)
- Reading the SW pin (16)
D0.OE = /CS0 & /SRD & /A18 & A17
Then it can read either the status of the switch at address 1F020018h or the status of the STB pin at 1F020010h
D0 =	STRB & /A2 & /A3 & A4 + // Strobe pin
		SW & /A2 & A3 & A4 // Switch pin
		
/XCVR_EN, pin 19, enables or disables the 74F245 transceiver
/XCVR_EN =	/CS0 & /SWR0 & /A2 & A3 & /A4 & A17 & A18 + // Write to commlink, 1F060008h
			/CS0 & /SRD & /A2 & /A4 & A17 & A18 // Read from commlink, 1F060000h

ACK, pin 15, is acting both as a way to notify something on the DSUB-25 that we are writing, and as a way to switch the 74F245 bus direction
ACK = /CS0 & /SWR0 & /A2 & A3 & /A4 & A17 & A18

/EEOE, pin 14, is connected to the /OE pin of the EEPROM, 1F000000h-1F01FFFFh / 1F040000h-1F05FFFFh
/EEOE = /CS0 & /SRD & /A17

/EEWR, pin 12, is connected to the /WR pin of the EEPROM, 1F000000h-1F01FFFFh / 1F040000h-1F05FFFFh
/EEWR = /CS0 & /SWR0 & /A17