Technical information

Read This First. OPTO DIO Reference
from a bit pattern written to the output port the 74LS541 chips
would have to be replaced by the inverting 74LS540 chips.
Remove the socketed 10k resistor networks.
Figure 1-8. Sink Driver Output Port Schematic._________________________________________
Figure 1-9. Sink Driver Output Connections._______________________________________
Chapter 1 Page 7