Current/voltage configurable I/O module having two D/A converters serially coupled together such that data stream flows through the first D/A to the second D/A

Claim 1

An I/O module for a programmable logic controller comprising: a first digital to analog converter including a data input and a data output, the first digital to analog converter further including a current output, a voltage output and range/mode select inputs; a second digital to analog converter including a data input and a data output, the second digital to analog converter further including a current output, a voltage output and range/mode select inputs, the data input of the second digital to analog converter being serially coupled to the data output of the first digital to analog converter; a serial to parallel shift register including a serial data input and a serial data output, the serial data output of the shift register being serially coupled to the data input of the first digital to analog converter, the shift register including first parallel range/mode select outputs coupled to the range/mode select inputs of the first digital to analog converter, the shift register further including second parallel range/mode select outputs coupled to the range/mode select inputs of the second digital to analog converter, such that a current output mode is individually selectable for one of the first and second digital to analog converters while a voltage output mode is individually selectable for the other of the first and second digital to analog converters; and a microprocessor for providing a serial data stream to the serial data input of the shift register such that data from the serial data stream is provided to the first parallel range/mode select outputs and the second parallel range/mode select outputs of the shift register to instruct the first and second digital to analog converters with respect to a mode to select and a range to select.