| 摘要 |
PURPOSE:To protect the data of an RAM, by separating the RAM from a power supply line of a decoder, providing a transfer gate between the RAM and the decoder, and connecting the area between the RAM and a gate to the power supply of the RAM via resistor. CONSTITUTION:The power of a battery 9 is supplied in series to a CPU1, an ROM2 and a decoder circuit 8 via a switch 10 and also in parallel to an RAM3. A transfer gate 11 is provided between the circuit 8 and a chip selecting terminal -CS of the RAM3. The power supply of the RAM3 is applied between the gate 11 and the terminal -CS through a resistor 12. The CPU1, ROM2 and decoder 8 are inactive when a switch 10 is off, and the gate 11 is cut off. In this case, the power supply voltage is applied to the RAM3 from the resistor 12 in order to protect the data of the RAM with a simple constitution and to reduce the power consumption. |
