Multi-mode protected memory
Multi-mode protected memory in accordance with the present description includes a permanent mode and a transient mode of operation. In one embodiment of the permanent mode, an authentication key is programmable once and a write counter is not decrementable or resettable. In one embodiment of the transient mode, an authentication key may be programmed many times and a write counter may be reset many times. Other features and advantages may be realized, depending upon the particular application.
1. An apparatus, comprising:
a protected memory; and
a protected memory controller to include circuitry configured to:
control access to the protected memory in a selected mode to include a transient mode and a permanent mode;
authenticate memory operations directed to the protected memory based on a re-programmable authentication key in the transient mode or based on a one-time programmable authentication key in the permanent mode;
maintain a resettable write counter value to indicate a count of write operations to the protected memory in the transient mode; and
maintain a non-resettable write counter value to indicate a count of write operations to the protected memory in the permanent mode.
2. The apparatus of claim 1 wherein the protected memory controller has further includes a register configured to be settable to indicate that the protected memory controller supports the transient mode.
3. The apparatus of claim 1 the protected memory controller further includes a fuse, wherein the circuitry is configured to set the fuse to disable entering the transient mode upon entering the permanent mode.
4. The apparatus of claim 1 wherein the protected memory controller further includes a re-programmable register configured to store the re-programmable authentication key in the transient mode, and a write-once register configured to store the one-time programmable authentication key in the permanent mode.
5. The apparatus of claim 1 wherein the protected memory controller is configured to respond to a transient mode set of request messages in the transient mode, and a permanent mode set of request messages in the permanent mode wherein an error response message is returned in response to receipt of a request message of the transient mode set of request messages when the protected memory controller is in the permanent mode.
6. A method, comprising:
controlling access to a protected memory in a selected mode including a transient mode in which memory operations directed to the protected memory are authenticated based on a re-programmable authentication key, or a permanent mode in memory operations directed to the protected memory are authenticated based on a one-time programmable authentication key;
resetting a resettable write counter value to indicate a count of write operations to the protected memory in the transient mode; and
counting, via a non-resettable write value, write operations to the protected memory in the permanent mode.
7. The method of claim 6 further comprising setting a register to indicate that the protected memory controller supports the transient mode.
8. The method of claim 6 further comprising setting a fuse to disable entering the transient mode upon entering the permanent mode.
9. The method of claim 6 further comprising storing the re-programmable authentication key in a re-programmable register in the transient mode, and storing the one-time programmable authentication key in a write-once register in the permanent mode.
10. The method of claim 6 further comprising responding to a transient mode set of request messages in the transient mode, responding to a permanent mode set of request messages in the permanent mode, and returning an error response message in response to receipt of a request message of the transient mode set of request messages when the protected memory controller is in the permanent mode.
11. A system, comprising:
a protected memory configured to store data;
a protected memory controller to include circuitry configured to:
control access to the protected memory in a selected mode to include a transient mode and a permanent mode;
authenticate memory operations directed to the protected memory based on a re-programmable authentication key in the transient mode or based on a one-time programmable authentication key in the permanent mode;
maintain a resettable write counter value to indicate a count of write operations to the protected memory in the transient mode; and
maintain a non-resettable write counter value to indicate a count of write operations to the protected memory in the permanent mode; and
a display configured to display information as a function of memory operations directed to the protected memory.
12. The system of claim 11 wherein the protected memory controller further includes a register configured to be settable to indicate that the protected memory controller supports the transient mode.
13. The system of claim 11 the protected memory controller further includes a fuse, wherein the circuitry is configured to set the fuse to disable entering the transient mode upon entering the permanent mode.
14. The system of claim 11 wherein the protected memory controller further includes a re-programmable register configured to store the re-programmable authentication key in the transient mode, and a write-once register configured to store the one-time programmable authentication key in the permanent mode.
15. The system of claim 11 wherein the protected memory controller is configured to respond to a transient mode set of request messages in the transient mode, and a permanent mode set of request messages in the permanent mode wherein an error response message is returned in response to receipt of a request message of the transient mode set of request messages when the protected memory controller is in the permanent mode.