| 摘要 |
<p>PURPOSE:To furnish method of operation of variable output power source for ROM that prevents destruction such as burn of ROM due to reverse insertion etc. by supplying voltage lower than normal power source voltage to a power source terminal at the time of first writing and thereby judging the state of insertion of ROM. CONSTITUTION:A microprocessor 1 outputs voltage Vr2 which is lower than normal writing voltage Vr1 from a variable output power source 2 for ROM to a power source terminal of ROM3. This current restriction characteristic becomes a curve shown by a dotted line. The microprocessor 1 reads voltage of a voltage terminal through a voltage measuring device 4 and compares it with a specified thershold value Vth. When mounting of ROM3 is correct, voltage of the voltage terminal becomes a high value Vgamma due to large load RL, and when ROM is inserted reversely becomes a low value Vbeta due to small load RL. The threshold value Vth is set between Vbeta and Vgamma, and when measured value is larger than Vth, it is judged as normal and normal writing operation is started. When the value is smaller than Vth, it is judeged that ROM3 is inserted reversely and reverse insertion state is displayed on a display device 5 and power feeding is finished.</p> |
