When you enable the advanced timestamp feature, the structure of the descriptor changes. The
advanced timestamp feature is supported only through the enhanced descriptors format. The
descriptor is 32-bytes long (eight words) and the snapshot of the timestamp is written in descriptor
TDES6 and TDES7.
Advanced Timestamp Receive Path Functions
When the advanced timestamp feature is enabled, the MAC processes the received frames to
identify valid PTP frames. The snapshot of the time sent to the application can be configured to:
■ Enable snapshot for all frames
■ Enable snapshot for IEEE 1588 version 2 or version 1 timestamp
■ Enable snapshot for PTP frames transmitted directly over Ethernet or UDP-IP-Ethernet
■ Enable timestamp snapshot for the received frame for IPv4 or IPv6
■ Enable timestamp snapshot only for EVENT messages (SYNC, DELAY_REQ, PDELAY_REQ,
or PDELAY_RESP)
■ Enable the node to be a master or slave and select the snapshot type. This controls the type of
messages for which snapshots are taken
The MAC provides the timestamp, along with EOF to the TX/RX Controller. The DMA returns the
timestamp inside the corresponding receive descriptor.
20.3.6
Frame Filtering
The following types of filtering are available for receive frames:
■ Source Address (SA) or Destination Address (DA) filtering
■ VLAN Filtering
The frame filtering supports a sequence where the packet is not forwarded to VLAN filtering if it
does not pass the SA or DA filtering first.
20.3.6.1
VLAN Filtering
The Ethernet MAC provides VLAN Tag Perfect Filtering and VLAN Tag Hash Filtering. In VLAN tag
perfect filtering, the MAC compares the VLAN tag of the received frame and provides the VLAN
frame status to the application. Based on the programmed mode of the
ETV
bit in the
EMACVLANTG
register, the MAC compares the lower 12 bits or all 16 bits of the received VLAN tag to determine
the perfect match. If VLAN tag perfect filtering is enabled, the MAC forwards the VLAN-tagged
frames along with VLAN tag match status and drops the VLAN frames that do not match. Inverse
matching for VLAN frames can also be enabled by setting the VTIM bit of the
Ethernet MAC VLAN
Tag (EMACVLANTG)
register, offset 0x01C. In addition, matching of S-VLAN tagged frames along
with the default C-VLAN tagged frames can be enabled by setting the
ESVL
bit of the
EMACVLANTG
register. The VLAN frame status bit (Bit 10 of RDES0) indicates the VLAN tag match status for the
matched frames.
Note:
The Source or Destination Address filter has precedence over the VLAN tag filters. A frame
which fails the Source or Destination Address filter is dropped irrespective of the VLAN tag
filter results.
1449
June 18, 2014
Texas Instruments-Production Data
Tiva
™
TM4C1294NCPDT Microcontroller