The G4D32EB2-UPG and G4EB2 I/O processors upgrade a legacy mistic or Pamux G4 digital I/O system on a serial network to operate as part of an Ethernet/TCP-based control system without needing to replace or modify existing I/O or field wiring. When upgraded, digital I/O can be accessed over a standard Ethernet network, and included as part of a control program or custom software application.