Hardware Bus Recovery Procedures for Stuck Open Drain Lines
Clear stuck open-drain lines using nine manual clock cycles, followed by power-rail cutoff via load switch when latchup bypasses clock release.
Bus Recovery
Functional Operation
Communication protocols operating on shared serial interfaces require automated mechanisms to restore stuck lines to an operational state. An automated sequence known as bus recovery addresses conditions where a subordinate device holds the data line low indefinitely, which halts all subsequent traffic. This corrective process typically executes by generating up to nine clock pulses on the serial clock line to force the hung device to release its grip on the bus.
Trigger Condition
Initiating this diagnostic action requires the controller to detect that the line has remained low for a period exceeding a specified timeout threshold. This condition typically arises when a controller is reset during an active read transaction. The slave device remains in a state of transmitting data, waiting for the clock signal that never arrives.
Recovery Protocol
Sending the sequential clock pulses prompts the stuck slave to release the data line by finishing its aborted byte transfer. Once the line rises high, the controller transmits a stop condition to reset the interface.
Validation Parameter
The timeout duration that triggers this corrective action is configured in milliseconds according to system requirements. A designer verifies the timing margin during board qualification. Proper execution of this sequence prevents system downtime.