PROM PROTECTING CIRCUIT FOR MISINSERTION OF PROM WRITER

摘要

PURPOSE:To facilitate an easy write-in/readout action to PROM and at the same time to prevent the breakdown due to a misinsertion of the PROM, by controlling the voltage to be supplied to the PROM and detecting the normal or abnormal insertion of the PROM into a socket through a comparator. CONSTITUTION:Transistors (TR) 3 and 2 are turned off since a voltage application signal 32 is set at OV excepting the write-in/readout mode. Then the voltage divided by a high resistance 1 and an internal resistance 7 of a PROM6 connected forward to a socket 4 is supplied to the PROM6. While the voltage passing through the resistance 1 is higher than the reference voltage, and the output of a comparator 5 is set at a low level. If the PROM6 is inserted backward into the socket 4, the resistance 7 is reduced. As a result, the output of the comparator 5 is inverted to a high level to produce an alarm through a buzzer 10, etc. In this case, both the voltage and current to be supplied to the PROM6 are controlled by the resistance 1 to prevent the destruction of the PROM6. Thus the write-in/readout to a PROM can be done in an easy and accurate way witout paying any excessive attention to the insertion of the PROM into a socket. At the same time, the breakdown of the PROM due to a misinsertion can be previously prevented.