Thin film magnetic memory device storing program information efficiently and stably
Each of program cell and memory cells includes a magnetic storage portion of the same configuration. The program cell further includes a state change portion. That is, the program cell has the same structure as the memory cell, except that the state change portion is additionally provided thereto. As such, the program cell can be provided efficiently, as it can be designed the same as the memory cell in terms of the magnetic storage portion and others. The state change portion makes a transition to a fixed state based on an electrical change. Thus, the state change portion prevents program information from being rewritten by a magnetic noise or the like, and ensures stable storage of the program information.
1. A thin film magnetic memory device, comprising:
a plurality of memory cells each storing data magnetically; and
a program cell storing program information used for said plurality of memory cells;
each of said memory cells and said program cell including a magnetic storage portion having an electric resistance value that changes according to a magnetization direction in accordance with a data write current, and
said program cell further including a state change portion having an electric resistance value that fixedly changes from a first state to a second state in response to an access designation externally supplied.
2. The thin film magnetic memory device according to claim 1 , wherein
said program cell includes
a first access element controlling electrical connection between said magnetic storage portion and a fixed voltage,
a second access element controlling electrical connection between said state change portion and a prescribed voltage, and
a conductor interconnection electrically coupling said first and second access elements to said magnetic storage portion, wherein
a first region of said conductor interconnection electrically couples said first access element to said magnetic storage portion,
a second region of said conductor interconnection electrically couples said first access element to said second access element, and
said second region of said conductor interconnection constitutes said state change portion.
3. The thin film magnetic memory device according to claim 2 , wherein said second access element controls the electrical connection of said state change portion with said prescribed voltage and said fixed voltage in response to said access designation externally supplied.
4. The thin film magnetic memory device according to claim 1 , wherein said program cell further includes an access element provided between a fixed voltage and a connect node connecting said magnetic storage portion and said state change portion.
5. The thin film magnetic memory device according to claim 1 , further comprising:
a plurality of said program cells arranged in rows and columns;
a plurality of bit lines provided corresponding to the columns respectively;
a plurality of write drivers provided corresponding to said plurality of bit lines, respectively, and each supplying a data write current to corresponding one of said plurality of bit lines in accordance with write data; and
a control circuit outputting said write data to at least two of said plurality of write drivers in parallel at the time of data write.
6. A thin film magnetic memory device, comprising:
a plurality of memory cells each storing data magnetically; and
a program cell storing program information used for said plurality of memory cells,
said program cell including
a plurality of state change portions each having an electric resistance changed in accordance with one of an externally supplied access designation and an applied magnetic field, and
at least one access element each connecting corresponding two of said state change portions in series with each other to a node to which a data read current is supplied at the time of data read.
7. The thin film magnetic memory device according to claim 6 , wherein
each said memory cell includes a magnetic storage portion having an electric resistance changed according to a magnetization direction, and
at least one of said plurality of state change portions is formed with said magnetic storage portion.
8. A thin film magnetic memory device, comprising:
a plurality of memory cells each storing data magnetically; and
a program cell storing program information used for said plurality of memory cells,
said program cell including
a plurality of state change portions each having an electric resistance changed in accordance with one of an externally supplied access designation and an applied magnetic field, and
a plurality of access elements provided corresponding to said plurality of state change portions, respectively, and each controlling electrical connection of the corresponding state change portion with one of a fixed voltage and a prescribed voltage,
said plurality of state change portions being provided corresponding to respective pieces of program data constituting said program information, and
said plurality of state change portions being set to electric resistance values independently from each other.
9. The thin film magnetic memory device according to claim 8 , wherein said plurality of state change portions store said program information of a plurality of bits.
10. The thin film magnetic memory device according to claim 8 , wherein one of said plurality of state change portions has a characteristic that its state changes reversibly in accordance with said applied magnetic field.