Processor maintaining reset-state after reset signal is suspended
Systems and techniques for processor reset hold control are described. A described system includes a controller to detect a hold request based on an external reset signal and an external debug signal, and generate a hold signal based on a detection of the hold request, where the hold signal continues after the external reset signal has been discontinued; a system component that is responsive to the external reset signal; a processor that is responsive to the hold signal, where the hold signal causes the processor to enter a reset state and to maintain the reset state after the external reset signal has been discontinued; and a system manager configured to permit external access to the system component while the processor is in the reset state. The controller can be configured to discontinue the hold signal in response to a clear request.
1. An integrated circuit apparatus comprising:
a first pad interface configured to receive an external debug signal;
a second pad interface configured to receive an external reset signal;
a controller configured to detect a hold request based on a combination of a first waveform associated with the external debug signal received at the first pad interface and a second waveform associated with the external reset signal received at the second pad interface, and to generate a hold signal and an internal reset signal based on a detection of the hold request;
a processor that is responsive to the external reset signal and the hold signal, wherein the external reset signal causes the processor to enter a reset state, wherein the hold signal causes the processor to maintain the reset state after the external reset signal has been discontinued, and wherein the generated internal reset signal is used by the controller to reset a system component; and
a system manager communicatively coupled with the controller and the system component, and configured to permit external access to the system component while the processor is in the reset state,
wherein the system manager is configured to send a clear request to the controller to clear the hold request, wherein the controller is configured to discontinue the hold signal in response to the clear request, and wherein the processor is configured to transition from the reset state to an active state based on a discontinuation of the hold signal.
2. The apparatus of claim 1 , wherein the system component includes a non-volatile memory, and wherein the system manager is configured to control a programming of the non-volatile memory while the processor is in the reset state.
3. The apparatus of claim 2 , wherein the system manager is configured to generate the clear request based on a completion of the programming of the non-volatile memory.
4. The apparatus of claim 1 , wherein the controller comprises one or more flip-flops to register the hold request once per a detection of the hold request, and wherein the clear request resets the one or more flip-flops such that the controller discontinues the hold signal.
5. The apparatus of claim 1 , wherein the system manager is configured to receive an external clear request and to generate the clear request based on the external clear request.
6. The apparatus of claim 1 , wherein the system manager includes a debug system.
7. The apparatus of claim 1 , further comprising:
a clock system that provides a clock signal to the controller.
8. The apparatus of claim 1 , wherein the controller is configured to combine the hold signal and the external reset signal to obtain a combined hold signal and reset signal and to provide the combined hold signal and reset signal to the processor, and
wherein the combined hold signal and reset signal causes the processor to enter the reset state when the external reset signal causes the system component to enter the reset state, and to maintain the reset state after the external reset signal has been discontinued.
9. The apparatus of claim 1 , further comprising circuitry coupled to the second pad interface and configured to combine the external reset signal and an internal signal to produce the internal reset signal,
wherein the internal signal comprises at least one of a power on reset signal or a brown-out detector signal.
10. The apparatus of claim 1 , wherein the controller is configured to detect the second waveform associated with the external reset signal by sensing a raising edge or a failing edge received at the second pad interface.
11. A system comprising:
a plurality of pad interfaces configured to receive signals including an external debug signal and an external reset signal;
a controller configured to detect a hold request based on a combination of a first waveform associated with the external debug signal and a second waveform associated with the external reset signal at the pad interfaces, and to generate a hold signal and an internal reset signal based on a detection of the hold request, wherein the hold signal continues after the internal reset signal has been discontinued;
a processor that is responsive to the hold signal, wherein the hold signal causes the processor to enter a reset state and to maintain the reset state after the internal reset signal has been discontinued, and wherein the generated internal reset signal is used by the controller to reset a system component; and
a system manager communicatively coupled with the controller and the system component, and configured to permit external access to the system component while the processor is in the reset state,
wherein the system manager is configured to send a clear request to the controller to clear the hold request, wherein the controller is configured to discontinue the hold signal in response to the clear request, and wherein the processor is configured to transition from the reset state to an active state based on a discontinuation of the hold signal.
12. The system of claim 11 , wherein the system component includes a non-volatile memory, and wherein the system manager is configured to control a programming of the non-volatile memory while the processor is in the reset state.
13. The system of claim 12 , wherein the system manager is configured to generate the clear request based on a completion of the programming of the non-volatile memory.
14. The system of claim 11 , wherein the controller comprises one or more flip-flops to register the hold request once per a detection of the hold request, and wherein the clear request resets the one or more flip-flops such that the controller discontinues the hold signal.
15. The system of claim 11 , wherein the system manager is configured to receive an external clear request and to generate the clear request based on the external clear request.
16. The system of claim 11 , wherein the system manager includes a debug system.
17. The system of claim 11 , further comprising:
a clock system that provides a clock signal to the controller.
18. A method comprising:
receiving signals that include an external debug signal and an external reset signal;
detecting a hold request based on a combination of a first waveform associated with the external debug signal received at a first pad interface and a second waveform associated with the external rest signal received at a second pad interface;
generating a hold signal and an internal reset signal based on a detection of the hold request, wherein the hold signal continues after the external reset signal has been discontinued;
operating one or more system components based on the generated internal reset signal by resetting the one or more system components using the generated internal reset signal;
operating a processor based on the hold signal, wherein the hold signal causes the processor to enter a reset state and to maintain the reset state after the external reset signal has been discontinued;
providing external access to the one or more system components while the processor is in the reset state; and
generating a clear request to discontinue the hold signal to cause the processor to transition from the reset state to an active state.
19. The method of claim 18 , wherein the one or more system component includes a non-volatile memory, and wherein providing external access comprises programming the non-volatile memory while the processor is in the reset state.
20. The method of claim 19 , wherein generating the clear request comprises generating the clear request based on a completion of the programming of the non-volatile memory.
21. The method of claim 18 , further comprising:
registering the hold request once per a detection of the hold request.