Interface Routing Circuitry for Quiescent Slave Data Buffering
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Solution Overview
Problem
Existing interconnect circuitry struggles to manage data transfers between master and slave devices when the slave device is in a quiescent mode, as it must accept the first data transaction without stalling or inhibiting its completion, while also allowing for power saving and maintaining data transaction order.
Innovation Solution
The interface employs routing circuitry that buffers data items when the slave device is in a quiescent mode, inhibiting further data transfers until the slave is ready, and switches to a direct path when the slave is active, ensuring compliance with protocols like AHB without introducing additional latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the slave device is put in quiescent mode to save power, then power consumption is reduced, but the device cannot receive data items
Solution Approach 1:
The interface detects when a slave device enters quiescent mode before data transfer is needed, and proactively buffers incoming data items in advance. This preliminary buffering action ensures that when the slave device wakes up, data is already ready for immediate transfer, eliminating the need to maintain continuous power while still ensuring data reception capability.
Solution Approach 2:
The interface acts as an intermediary between the master device and the slave device in quiescent mode. It receives data items from the master device, buffers them temporarily, and then transfers them to the slave device when ready. This intermediary buffering mechanism allows the slave device to remain in low-power quiescent mode while still maintaining reliable data reception through the interface's mediation.
2Reliability
If data is buffered when slave device is quiescent, then data integrity is maintained, but data transfer latency increases
Solution Approach 1:
Data buffering is performed in advance while the slave device is in quiescent mode, so that when the device wakes up, data is already prepared and ready for immediate transfer. This preliminary action eliminates the need for data to wait after wake-up, thereby maintaining data integrity while minimizing actual transfer latency.
Solution Approach 2:
The interface dynamically switches between two data paths based on the slave device's state: using the first data path through the buffer when the slave is quiescent, and using the second direct data path when the slave is active and ready. This dynamic path selection optimizes both data integrity (by buffering when necessary) and transfer speed (by using direct path when possible).
3Reliability
If protocol requires first data transaction to be accepted, then protocol compliance is ensured, but device must remain active increasing power consumption
Solution Approach 1:
The interface serves as a protocol-compliant intermediary that accepts data transactions from the master device even when the slave device is in quiescent mode. It buffers the first data transaction and subsequent transactions, ensuring protocol compliance at the interface level while allowing the slave device to remain in low-power mode, thus maintaining protocol compliance without requiring continuous slave device activation.
Solution Approach 2:
The interface performs preliminary acceptance and buffering of data transactions before the slave device needs to wake up. This allows the system to comply with protocol requirements for accepting transactions while the slave remains in quiescent mode, as the interface handles the protocol compliance requirements in advance.
Data Source
AI summary
An interface comprises routing circuitry configured to receive data items from a data source device and to route the received data items to a data sink device by either a first data path including a data buffer or a second data path, in response to an indication of a current state of a data sink device; the routing circuitry being configured to route the received data item by the first data path and to initiate a transition of the data sink device to a ready state in response to an indication that the data sink device is in a quiescent mode and currently not ready to receive the data item, the routing circuitry being configured to hold the data item at the buffer and to inhibit the data source device from sending further data items until the routing circuitry receives a subsequent indication that the data sink device is ready to receive the data item; and the routing circuitry being configured to route the received data item by the second data path in response to an indication that the data sink device is currently ready to receive the data item.