A circuit (50, 80) for configuring a plurality of I/O modules of a fieldbus controller, wherein each of the plurality of I/O modules can be configured separately, the circuit comprising: a digital input of each of the plurality of I/O modules, wherein the digital input is configurable as either a PNP input or an NPN input, a control circuit comprising, for each of the plurality of I/O modules: a reference input for receiving a reference voltage; a first selection input for electronically selecting either an NPN mode or a PNP mode of the digital input, wherein an electronic state of the first selection input controls a voltage provided at the reference input; a control output for providing an electronic command indicative of either the NPN mode or the PNP mode, wherein the electronic command provided by the control output corresponds to the voltage provided at the reference input; and a data circuit, comprising: a second selection input electrically connected to the control output for receiving the electronic command provided by the control output, wherein the second selection input is operative to electronically configure the digital input as either a PNP input or an NPN input depending on the electronic command received by the control output; a data input electrically coupled to the digital input; and a data output for providing data corresponding to the data input, wherein the control output is operative to electronically connect the second selection input to one of a first voltage level or a second, different voltage level. a digital input of each of the plurality of I/O modules, wherein the digital input is configurable as either a PNP input or an NPN input, a control circuit comprising, for each of the plurality of I/O modules: a reference input for receiving a reference voltage; a first selection input for electronically selecting either an NPN mode or a PNP mode of the digital input, wherein an electronic state of the first selection input controls a voltage provided at the reference input; a control output for providing an electronic command indicative of either the NPN mode or the PNP mode, wherein the electronic command provided by the control output corresponds to the voltage provided at the reference input; and a reference input for receiving a reference voltage; a first selection input for electronically selecting either an NPN mode or a PNP mode of the digital input, wherein an electronic state of the first selection input controls a voltage provided at the reference input; a control output for providing an electronic command indicative of either the NPN mode or the PNP mode, wherein the electronic command provided by the control output corresponds to the voltage provided at the reference input; and a data circuit, comprising: a second selection input electrically connected to the control output for receiving the electronic command provided by the control output, wherein the second selection input is operative to electronically configure the digital input as either a PNP input or an NPN input depending on the electronic command received by the control output; a data input electrically coupled to the digital input; and a data output for providing data corresponding to the data input, a second selection input electrically connected to the control output for receiving the electronic command provided by the control output, wherein the second selection input is operative to electronically configure the digital input as either a PNP input or an NPN input depending on the electronic command received by the control output; a data input electrically coupled to the digital input; and a data output for providing data corresponding to the data input, wherein the control output is operative to electronically connect the second selection input to one of a first voltage level or a second, different voltage level.