Shared Memory Arbitration Using Existing Pins and Auto-Refresh
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Solution Overview
Problem
Existing arbitration schemes for shared memory devices require additional I/O pins and introduce time delays due to software complexity and the need for UART interfaces, especially as the number of masters increases.
Innovation Solution
The solution involves using existing pins to send request for access and acknowledge signals concurrently with the transmission of an indispensable command, such as an auto-refresh command, synchronized with a master clock signal, to efficiently arbitrate access among multiple masters without requiring additional pins or interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate request and acknowledge signals are used for arbitration, then access control among multiple masters is achieved, but additional I/O pins are required
Solution Approach 1:
The patent merges the request signal and acknowledge signal into a single bidirectional signal line. The master and slave exchange arbitration information through one pin by using different signal levels or timing to distinguish between request and acknowledge phases, thereby eliminating the need for separate dedicated pins for each function.
Solution Approach 2:
The arbitration signal line serves multiple functions: it acts as both a request line (when driven by the master) and an acknowledge line (when driven by the slave). This multi-functional approach allows the same physical pin to handle both directions of communication, reducing the total pin count while maintaining full arbitration capability.
2Reliability
If separate request and acknowledge signals are used for arbitration, then access control among multiple masters is achieved, but time delay is introduced
Solution Approach 1:
By combining request and acknowledge signals into a single bidirectional exchange, the patent eliminates the sequential timing delays associated with separate signal lines. The master and slave can complete the entire arbitration handshake through one integrated signal transaction, reducing the overall time required for access control.
3Ease of operation
If additional I/O pins are used for arbitration signals, then request and acknowledge communication is enabled, but pin count increases
Solution Approach 1:
The patent makes the arbitration signal line universal by enabling it to function as both request and acknowledge carrier. This multi-functionality allows complete arbitration communication to be achieved through a single pin, eliminating the need for additional dedicated pins while maintaining full operational capability.
Data Source
AI summary
For arbitrating access to a shared memory device among a plurality of masters, a master generates a request for access signal that is sent to the arbitrator concurrently with an indispensable command such as an auto-refresh command that is generated in series. The arbitrator generates an acknowledge signal sent to the master for indicating approval or rejection for access. Existing pins of the master are used for transmission of such arbitration signals.