Datasheet

program the width and interval to values 1 and 2, respectively. Note that the PPS0WIDTH and
PPS0INT value must be programmed as one less than the required interval. Before giving the
command to trigger a pulse or pulse train on the EN0PPS output, the interval and width of the PPS
signal output should be programmed or updated.
Advanced Timestamp Transmit Path Functions
The only aspect of the transmit path that changes with advanced timestamp is the descriptor, which
extends to 32-bytes long.
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.
24.3.8 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.
24.3.8.1 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
1639December 13, 2013
Texas Instruments-Advance Information
Tiva
™
TM4C129XNCZAD Microcontroller