| 摘要 |
PURPOSE:To reduce the current consumption in order to hold the contents of a D-RAM by securing an optimum refresh mode or interval of the D-RAM according to the supplied power supply voltage or the ambient temperatures or both of them. CONSTITUTION:A SUB CPU9 turns on a transistor TR13 and reads out the data on an A/D converter 8. The temperature information is obtained from the voltage of a thermistor 6; while the information on the power supply voltage impressed to a D-RAM11 is obtained from the voltage of a resistance 7 respectively. Based on these information, the SUB CPU9 calculates both optimum refresh mode and interval corresponding to the characteristics of the RAM11. Receiving this calculation output, a D-RAM control signal generating circuit 10 produces a signal needed for refresh and delivers it to the RAM11. Then the SUB CPU9 is kept under a pause state and the power supply is cut off to the converter 8. However the SUB CPU9 restarts its actuation periodically to update the output to the circuit 10 since both the temperature and the voltage vary with the time lapse. |
