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B.5 Bus ISR Settings

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Roland Jax edited this page Sep 26, 2026 · 1 revision

B.5 Bus ISR Settings

When configuring bus operation, the Bus ISR Window and the Bus ISR Offset are crucial parameters that influence the timing and effectiveness of Interrupt Service Routines (ISRs).

The Bus ISR Window defines the time period within which bus access attempts must be made. The Bus ISR Offset compensates for processing delays, thus ensuring precise timing alignment with the desired window.

Careful adjustment of these parameters is essential to optimize the performance and reliability of communication protocols and enable smooth data transmission. Correct configuration contributes to the stability and responsiveness of the overall system.

Parameter Descriptions

  • Bus ISR Window (microseconds): The time window in which bus access attempts should occur after the falling edge of the start bit of the synchronization symbol. This value should be in the range of 4300 to 4456 microseconds. Recommended starting value: 4300 microseconds.

  • Bus ISR Offset (microseconds): An adjustment value that compensates for delays in the ISR, ensuring precise timing relative to the bus ISR window. Recommended starting value: 70 microseconds.

These values provide a baseline for optimizing bus operation performance, with specifications indicating that the start edge of the source address must appear on the bus after the expiration of the access time interval. Proper synchronization following the SYN symbol is essential for the arbitration procedure to function correctly.

How to Check Bus ISR Settings

  • Ensure Active Commands: Verify that at least one active command is installed. This is essential for the Bus ISR to attempt a bus request.

  • Access Statistics Page: Navigate to the statistics page to observe relevant metrics.

  • Timing: Look for the BusIsr timing values. The mean value should be close to your desired settings (e.g., around 4300 to 4456 microseconds for the Bus ISR Window).

  • Counter: Review the counter page, focusing on the sections for reset and error.

    • Resets may indicate conflicts on the bus, often resulting from poor timing or concurrent bus access attempts.

    • Errors typically indicate malformed messages. Ensure that the active error counters are zero, which suggests no issues with the bus operation.

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