MCU OVERLOAD

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The MCU OVERLOAD block detects when scheduled tasks miss their execution deadlines.

When to use:

When to use:

• Hard real-time deadlines must be enforced (safety-critical applications)
• Detecting task overruns needed for diagnostics or fault handling
• Triggering recovery action on deadline miss (safe state, error log)
• Profiling application to identify occasional overload conditions
• Verifying scheduler configuration before production deployment

When NOT to use:

• Soft timing requirements — occasional deadline misses acceptable
• CPU always has sufficient margin (overload never occurs)
• No action taken on overload detection — block output unused
• Prefer MCU LOAD block for general utilization monitoring

Overview

The MCU OVERLOAD block monitors the multitasking scheduler for deadline violations. It outputs a bitmask indicating which task(s) experienced overload and optionally drives a GPIO pin high when any overload occurs.

Block Dialog

Ports

Outputs

Parameters

Output Signal Format

The block output is a 16-bit bitmask where each bit represents the overload status of a task ID (TID):

Bit 0  → TID 0 (base rate - fastest task)
Bit 1  → TID 1
Bit 2  → TID 2
...
Bit 15 → TID 15 and higher

Reading the output clears the overload status.

GPIO Pin Behavior

When configured, the GPIO pin is set high asynchronously when any overload occurs. The pin remains high until explicitly cleared using a Digital Output block writing 0 to the same pin.

Implementation Details

Overload Detection

The block uses a volatile union containing individual bit fields for each task:

union {
  struct {
    unsigned int task0 : 1;
    unsigned int task1 : 1;
    // ... up to task15
  } b;
  unsigned int val;
} volatile MCHP_MCU_Overload;

Output Behavior

MultiTasking mode:

• Uses XOR to atomically read and clear the overload status (protection from simultaneous access)

SingleTasking mode:

• Direct read of status value, then clear to 0

Related Blocks

• MCU LOAD - CPU utilization monitoring
• Tasks State - Task execution monitoring