초록 ▼

A method of determining the condition of a battery which backs up a real-time clock (RTC) when a main power supply fails or is disconnected, in a system which includes a controller having a volatile random access memory (VRAM) and a non-volatile random access memory (NVRAM). The method includes the

A method of determining the condition of a battery which backs up a real-time clock (RTC) when a main power supply fails or is disconnected, in a system which includes a controller having a volatile random access memory (VRAM) and a non-volatile random access memory (NVRAM). The method includes the steps of periodically storing the time value of the RTC in NVRAM, and periodically writing a predetermined data pattern in VRAM, while the main power supply adequately powers the real time clock. The method then includes the steps of detecting a power-down condition of the main power supply, and terminating the recording and writing steps when the detecting step detects power-down. Return of main power, or power-up, is then detected, with the data pattern stored in VRAM then being compared with the predetermined data pattern. When the patterns are not the same, indicating more than a transitory loss of main power, the difference between the time value indicated by the RTC upon power-up and the last time value of the RTC stored in NVRAM before power down is compared with a predetermined constant time value. When the RTC has not incremented by at least the predetermined constant time value the method includes the step of indicating that the back-up battery is bad.

대표청구항 ▼

A method of determining the condition of a battery which backs up a real-time clock (RTC) when a main power supply for the RTC fails or is disconnected, comprising the steps of: storing a time value of the RTC in non-volatile memory means while powered by the main power supply, just prior to a loss

A method of determining the condition of a battery which backs up a real-time clock (RTC) when a main power supply for the RTC fails or is disconnected, comprising the steps of: storing a time value of the RTC in non-volatile memory means while powered by the main power supply, just prior to a loss of the main power supply, detecting return of the main power supply, comparing the time value of the RTC upon return of the main power supply with said stored time value of the RTC, and indicating that the back-up battery is bad when the comparison step finds a predetermined relationship between the compared time values.