Method and circuit for brownout detection in a memory system

A system, comprising:

• a non-volatile memory (NVM) having contents that are sequentially addressable;
• sensing circuitry able to sense data in the NVM using a first reference for a normal read mode, a second reference for a first test read mode in which detecting a logic high is at higher standard than the normal read mode, and a third reference for a second test read mode in which detecting a logic low is at higher standard than the normal read mode;
• and
• a memory controller for:
• loading the contents of the NVM by sequential addressing;
• identifying a pair of adjacent locations in the NVM in which one location of the pair of adjacent locations is filled with possible data and another location of the pair of adjacent locations is empty using the sensing circuitry in the normal read mode;
• determining the contents of a first location of the pair using the sensing circuitry in the first test read mode to obtain a first test value;
• determining the contents of the first location of the pair using the sensing circuitry in the second test read mode to obtain a second test value;
• determining if the first test value is the same as the second test value;
• and
• if the first test value is the same as the second test value, for:
• determining the contents of a second location of the pair using the sensing circuit in the first test read mode to obtain a third test value;
• determining the contents of the second location using the sensing circuit in the second test read mode to obtain a fourth test value;
• determining if the third test value is the same as the fourth test value, and
• identifying that a brownout has occurred if a determination comprising one of a group consisting of the first test value is different than the second test value and third test value is different than the fourth test value is made.

A method, comprising:

• providing a random access memory (RAM);
• providing non-volatile memory (NVM);
• loading the RAM with valid data;
• loading the NVM with data corresponding to the valid data, wherein the manner of loading the NVM is sequential according to sequential addresses of the NVM so that there is a pair of locations comprising a last filled location and an empty location sequential to the last filled location;
• determining the pair of locations using a first reference for sensing contents of the pair of locations;
• determining if a first location of the pair of locations has experienced a brownout, comprising:
• determining the contents of the first location as a first value using a second reference for sensing, wherein the second reference sets a higher standard for determining a logic high than the first reference;
• determining the contents of the first location as a second value using a third reference for sensing, wherein the third reference sets a higher standard for determining a logic low than the first reference;
• comparing the first value to the second value;
• if the first value is different from the second value, identifying that a brownout has occurred;
• if the first value is the same as the second value, perform further steps, comprising:
• determining the contents of the second location as a third value using the second reference for sensing;
• determining the contents of the second location as a fourth value using the third reference for sensing;
• comparing the third value to the fourth value;
• if the third value is different from the fourth value, identifying that a brownout has occurred;
• and
• if the third value is the same as the fourth value, identifying that a brownout has not occurred.