ROM CODE CHECKING CIRCUIT

摘要

PURPOSE:To enable the reading of a ROM code number data with a data bus. CONSTITUTION:This circuit has a first group of transistors 11 connected in series to a data bus 9 allowed to read externally and second groups 12 and 13 of transistors connected in series to the first group of transistors 11 separately. It is so arranged that output voltages of the second group 11 of transistors in which a threshold voltage is varied selectively beforehand in a production process can be read out as ROM code number data through the first group 11 of transistors which is ON or OFF controlled by a specified reading signal.