Intel® Agilex™ Hard Processor System Technical Reference Manual

ID 683567
Date 11/11/2022
Public

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17.6.2.5.4. Transmit Polling Suspended

Transmit polling can be suspended by either of the following conditions: †

  • The DMA detects a descriptor owned by the Host (TDES0[31]=0). To resume, the driver must give descriptor ownership to the DMA and then issue a Poll Demand command. †
  • A frame transmission is aborted when a transmit error because of underflow is detected. The appropriate Transmit Descriptor 0 (TDES0) bit is set. †

If the DMA goes into SUSPEND state because of the first condition, then both Bit 16 (Normal Interrupt Summary) and Bit 2 (Transmit Buffer Unavailable) of Register 5 (Status Register) are set. If the second condition occur, both Bit 15 (Abnormal Interrupt Summary) and Bit 5 (Transmit Underflow) of Register 5 (Status Register) are set, and the information is written to Transmit Descriptor 0, causing the suspension. †

In both cases, the position in the transmit List is retained. The retained position is that of the descriptor following the Last descriptor closed by the DMA. †

The driver must explicitly issue a Transmit Poll Demand command after rectifying the suspension cause. †