Abstract: In certain aspects of the disclosure, a system includes an isolation device coupled between a first circuit in a first power domain and a second circuit in a second power domain. The system also includes a second power source coupled to a power distribution network, wherein the power distribution network is configured to distribute power from a first power source to the second power domain. The system further includes a failure detector having an input coupled to a node on the power distribution network located upstream of the second power source, and an output coupled to the isolation device, wherein the failure detector is configured to sense a voltage at the node, to detect a power loss of the first power source based on the sensed voltage, and to enable the isolation device in response to detection of the power loss.

Abstract: In certain aspects of the disclosure, a system includes an isolation device coupled between a first circuit in a first power domain and a second circuit in a second power domain. The system also includes a second power source coupled to a power distribution network, wherein the power distribution network is configured to distribute power from a first power source to the second power domain. The system further includes a failure detector having an input coupled to a node on the power distribution network located upstream of the second power source, and an output coupled to the isolation device, wherein the failure detector is configured to sense a voltage at the node, to detect a power loss of the first power source based on the sensed voltage, and to enable the isolation device in response to detection of the power loss.

Abstract: In certain aspects of the disclosure, a chip includes an isolation device, wherein the isolation device is configured to allow a signal to pass from a first circuit in a first power domain to a second circuit in a second power domain via a signal line that crosses between the first and second power domains when the isolation device is disabled, and to clamp a portion of the signal line in the second power domain to a logic state when the isolation device is enabled. The chip also includes a failure detector configured to detect an imminent power failure of at least one of the first power domain or the second power domain, and to enable the isolation device in response to detection of the imminent power failure.

Abstract: In certain aspects of the disclosure, an apparatus includes first and second semaphore registers disposed in a first power domain. A common address bus is coupled to the first and second semaphore registers, and a semaphore lock is disposed in the first power domain and coupled to the first and second semaphore registers. The semaphore lock is controlled by the first and second semaphore registers, and controls whether a signal from a second power domain is permitted to propagate to the first power domain. The first and second semaphore registers may be associated with first and second register addresses, respectively, which are selected to provide a substantially maximized Hamming distance between them. The first and second semaphore registers may have a write order expectation enforced between them.

Abstract: In certain aspects of the disclosure, an apparatus includes first and second semaphore registers disposed in a first power domain. A common address bus is coupled to the first and second semaphore registers, and a semaphore lock is disposed in the first power domain and coupled to the first and second semaphore registers. The semaphore lock is controlled by the first and second semaphore registers, and controls whether a signal from a second power domain is permitted to propagate to the first power domain. The first and second semaphore registers may be associated with first and second register addresses, respectively, which are selected to provide a substantially maximized Hamming distance between them. The first and second semaphore registers may have a write order expectation enforced between them.

Abstract: In certain aspects of the disclosure, a chip includes an isolation device, wherein the isolation device is configured to allow a signal to pass from a first circuit in a first power domain to a second circuit in a second power domain via a signal line that crosses between the first and second power domains when the isolation device is disabled, and to clamp a portion of the signal line in the second power domain to a logic state when the isolation device is enabled. The chip also includes a failure detector configured to detect an imminent power failure of at least one of the first power domain or the second power domain, and to enable the isolation device in response to detection of the imminent power failure.