ASSOCIATIVE STORAGE DEVICE SYSTEM AND PROGRAMMABLE READ-ONLY MEMORY

摘要

PURPOSE: To correctly operate an associative memory device in both of reading- out and program modes by changing over the first and second bias voltages applied to this device by a selector switch according to the detection results of the first and second source voltages supplied to the device. CONSTITUTION: The respective detecting circuits 48 or 50 and 60 output signals 49, 52, 62 when these circuits detect the source voltages Vcc or Vpp , in both reading-out and programming modes of the EPROM of the associative memory device. The sure and adequate operation of both modes is executed by a latch 14 and the spare columns and rows 30 and 32 of a ROM 18 are exactly addressed by the reset signal 42 outputted from an OR gate 64 by these signals. The switch 58 selects the adequate bias voltage 54 or 56 for both modes to be inputted and outputs the voltages to a UPROM 12 by the signal 52. As a result, the ROM 18 is programmed by the low source voltage, by which power source consumption is reduced. The ROM is operated by the high voltage during the programming. The correct operation is thus executed at multiple power source levels.