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

摘要

A current/voltage configurable I/O module is provided for a programmable logic controller. The I/O module includes first and second D/A converters which are cascaded together such that a data stream provided to the first D/A converter flows through to the second D/A converter. Each of the D/A converters includes a respective current output, a voltage output and range/mode select inputs. A serial to parallel shift register is coupled between a microprocessor data output and the data input of the first D/A converter such that information from a data stream supplied by the microprocessor is passed in serial fashion to the first and second D/A converters. The shift register also includes parallel outputs, namely range/mode select outputs, to which range/mode select information from the data stream is provided. The range/mode select outputs of the shift register are coupled to the range/mode select inputs of the first and second D/A converters such that the range/mode select information can instruct the first and second D/A converters with respect to a current/voltage mode and a current/voltage range to employ. In this manner, the range and mode of the I/O module can be readily configured and reconfigured as desired.