| 摘要 |
<p>A 3-state bidirectional buffer (6) is directly connected with a data bus or a PROM, and it comprises a voltage dropping means (22) which inputs the program power-supply voltage supplied to the PROM, then drops the input program power-supply voltage (Vpp), and a bidirectional bus control means (20a to 20e; 21a, 21b, 24, 48; 25a and 25b; 26 to 29 and 44) which controls the direction of the data bus on the basis of the program power-supply voltage dropped and the program input signal supplied to the PROM. A portable semiconductor storage device comprises such a 3-state bidirectional buffer inserted in a data bus for at least one PROM, and a buffer means through which a program input signal is supplied from an external circuit to the PROM. <IMAGE></p> |
