4.4.1. Padding Bytes Insertion
By default, the MAC TX inserts padding bytes (0x00) into TX frames to meet the following minimum payload length:
- 46 bytes for basic frames
- 42 bytes for VLAN tagged frames
- 38 bytes for stacked VLAN tagged frames
Ensure that CRC-32 insertion is enabled when padding bytes insertion is enabled.
You can disable padding bytes insertion by setting the tx_pad_control register to 0. When disabled, the MAC IP core forwards the frames to the PHY-side interface without padding. Ensure that the minimum payload length is met; otherwise the current frame may get corrupted. You can check for undersized frames by referring to the statistics collected.