| 摘要 |
A multistate ROM (10) is described having memory cells (14) that each comprise one of four types of transistors (40). A first type has a threshold voltage of Vt1, a second type has a voltage threshold of Vt2, a third type has a threshold voltage of Vt3, and a fourth type has a threshold voltage of Vt4. When the ROM (10) is addressed, an internal line driver selectively applies a first voltage Vg1, greater than Vt1, to the addressed cell (14). If a sensing amplifier (16) determines the transistor (40) is on, the sensing amplifier (16) outputs a "00" state on the ROM output data pins (18). If the transistor (40) is off, the line driver applies a higher second voltage Vg2, greater than Vt2, to the addressed cell (14). If a sensing amplifier (16) determines the transistor (40) is on, the sensing amplifier (16) outputs a "01" state.
|
