Method for EEPROM write protection using threshold voltage projection
First Claim
1. In a microprocessor based system having an EEPROM wherein a minimum supply voltage is required for writing to the EEPROM, and the supply voltage is derived from battery voltage and decreases when the battery voltage drops below a known low voltage;
- the method of preventing a write cycle in the absence of adequate voltage comprising the steps of;
determining a battery voltage threaded which correspond to the required minimum supply voltage;
measuring the battery voltage at the time for beginning the write cycle;
determining a time rate of change for the battery voltage;
projecting the battery voltage to the end of the write cycle; and
canceling the write cycle when the projected battery voltage at the end of the cycle is below the battery voltage threshold.
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Abstract
Writing to an EEPROM when the regulated supply voltage to the EEPROM is below a minimum voltage required for proper operation is prevented by determining the battery voltage threshold which corresponds to the minimum required supply voltage, measuring the battery voltage and the rate of change of voltage and projecting the voltage to the end of the write cycle. When the projected battery voltage is below the threshold the write cycle is canceled. The write cycle is also canceled when the battery voltage is below the normal operating range when a write cycle is requested.
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Citations
7 Claims
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1. In a microprocessor based system having an EEPROM wherein a minimum supply voltage is required for writing to the EEPROM, and the supply voltage is derived from battery voltage and decreases when the battery voltage drops below a known low voltage;
- the method of preventing a write cycle in the absence of adequate voltage comprising the steps of;
determining a battery voltage threaded which correspond to the required minimum supply voltage; measuring the battery voltage at the time for beginning the write cycle; determining a time rate of change for the battery voltage;
projecting the battery voltage to the end of the write cycle; andcanceling the write cycle when the projected battery voltage at the end of the cycle is below the battery voltage threshold.
- the method of preventing a write cycle in the absence of adequate voltage comprising the steps of;
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2. In a microprocessor based system having an EEPROM wherein a minimum supply voltage is required for writing to EEPROM, and the supply voltage is derived from battery voltage and decreases when the battery voltage drops below a known low voltage;
- the method of preventing a write cycle in the absence of adequate voltage comprising the steps of;
determining a battery voltage minimum threshold which corresponds to the required minimum supply voltage; measuring the battery voltage at a time prior to beginning a write cycle; calculating a time rate of change for the battery voltage; projecting the battery voltage to the end of the write cycle; canceling the write cycle when the projected battery voltage at the end of the write cycle is below the battery voltage minimum threshold; and starting the write cycle when the projected battery voltage at the end of the cycle is at or above the battery voltage minimum threshold. - View Dependent Claims (3, 4)
- the method of preventing a write cycle in the absence of adequate voltage comprising the steps of;
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5. In a microprocessor based system having an EEPROM wherein a minimum supply voltage is required for writing to the EEPROM, and the supply voltage is derived from battery voltage and decreases when the battery voltage drops below a known low voltage;
- the method of preventing a write cycle in the absence of adequate voltage comprising the steps of;
determining a battery voltage threshold which corresponds to the required minimum supply voltage; measuring a battery voltage V0 at a period P1 prior to beginning a write cycle; measuring a battery voltage V1 at a time for beginning the write cycle; estimating a projected battery voltage Vest at the end of the write cycle by the equation Vest=V1+((V1-V2)/P1)P2 where P2 is the EEPROM write period; and canceling the write cycle when the projected battery voltage at the end of the write cycle is below the battery voltage threshold. - View Dependent Claims (6, 7)
- the method of preventing a write cycle in the absence of adequate voltage comprising the steps of;
Specification