PROGRAMMABLE MONOLITHIC INTEGRATED CIRCUIT

PURPOSE:To prevent the acceleration of reading-out speed due to reduction of input/ output capacity as well as the erroneous operation after writing-in from occuring by a method wherein a means to isolate a control circuit for testing ambient circuits from an input of the control circuit and another means to isolate a writing-in circuit from an input of the writing-in circuit are provided. CONSTITUTION:The title integrated circuit is provided with a means to isolate an input of a writing-in circuit WC from the writing-in circuit and another means to isolate an input of a control circuit provided for testing ambient circuits from the control circuit. For example, when an input IN1 of gate G1 is kept at high level while an output of gate G1 at low level to supply an output terminal Om with current while maintaining an output circuit OC to isolate any needless writing-in circuit from the output terminal Om after writingin a fixed memory element in an inert state, the current flows in the gate G1 through fuse elements 1 due to the low level of output from gate G1. At this time, the fuse elements 1 are melted down by supplying the fuse elements 1 with sufficient current to isolate the output terminal Om from the writing-in current. Likewise, an input terminal An can be isolated from a test circuit TC.