TM4C129XKCZAD Datasheet, PDF (1636/2188 Pages) Texas Instruments – Tiva Microcontroller

Ethernet Controller
■ Insert the content of the MAC Address Registers in the SA field.
■ Replace the content of the SA field with the content of the MAC Address Registers.
The software can enable the SA insertion or replacement for all transmitted frames or selective
frames:
■ To enable SA insertion or replacement feature for all frames, program the SADDR field of the
Ethernet MAC Configuration (EMACCFG) register.
■ To enable SA insertion or replacement for selective frames, program the SA Insertion Control
field (TDES1 Bits [31:29]) in the first transmit descriptor of the frame. When Bit 31 of TDES1 is
set, the SA Insertion Control field indicates insertion or replacement by MAC Address1 registers.
When Bit 31 of TDES1 is reset, it indicates insertion or replacement by MAC Address 0 registers.
When SA insertion is enabled, the application should ensure that the frames that are sent to the
MAC do not have the SA field. The MAC does not check the presence of SA field in the transmit
frame and just inserts the content of MAC Address Registers in the SA field. Similarly, when SA
replacement is enabled, the application should ensure that the frames that are sent to the MAC
have the SA field. The MAC just replaces the six bytes, following the Destination Address field in
the transmit frame, with the content of the MAC Address Registers.
24.3.8.2
VLAN Insertion, Replacement or Deletion
The software can use the VLAN insertion, replacement, or deletion feature to instruct the MAC to
do the following for transmit frames:
■ Insert or replace the VLAN Type field (C-VLAN or S-VLAN indicated by the CSVL bit of the
Ethernet MAC VLAN Tag Inclusion or Replacement (EMACVLNINCREP), MAC offset 0x584)
and the VLAN Tag field in the transmit frame with the VLT field of the EMACVLNINCREP register.
■ Delete the VLAN Type and VLAN Tag fields in the transmit frame.
The software can enable the VLAN insertion, replacement, or deletion feature for all transmitted
frames or selective frames. To enable this function for all transmit frames, configure the VLT field
in the EMACVLNINCREP register.
When VLAN replacement or deletion is enabled, the MAC checks the presence of the VLAN Type
field (0x8100 or 0x88a8), after the Destination address (DA) and SA fields, in the transmit frame.
The replace or delete operation does not occur if the VLAN Type field is not detected in the two
bytes following the DA and SA fields. However, when VLAN insertion is enabled, the MAC does not
check the presence of VLAN Type field in the transmit frame and just inserts the VLAN Type and
VLAN Tag fields.
24.3.8.3
CRC Replacement
The software can use the CRC replacement feature to instruct the MAC to replace the FCS field in
the transmit frame with the CRC computed by the MAC. This feature works on a per-frame basis.
The CRC replacement control field in the Transmit Descriptor Word 0 (TDES0) can be programmed
to enable this for a frame. This feature is valid only when the Disable CRC control (Bit 27 of TDES0)
is enabled. If SA or VLAN insertion control is enabled, the MAC appends or replaces the FCS field
with the computed CRC when Disable CRC Control is enabled or disabled, respectively.
1636
Texas Instruments-Production Data
June 18, 2014