Input interface unit for programmable logic controller

An input interface unit for a programmable logic controller comprising plural input terminals divided into plural groups to which external switches are to be connected;

• a current-voltage converter circuit provided for each of said groups of input terminals for converting current signals applied to each of said input terminals to voltage signals;
• plural output terminals connected to input bus lines of a central control unit (CPU) to which outputs from said current-voltage converter circuit are led;
• generating group assignment data input terminals connected to control bus lines of the central control unit (CPU), and a power supply controlling means which allows supply of power for converting operation only to said current-voltage converter circuit for specific terminal groups corresponding to the contents of the generating group assignment data applied to said generating group assignment data input terminals.