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Functional Description
922
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Ethernet Controller
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Cancellation of the programmed EN0PPS start or stop request.
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Error indication if the start or stop time being programmed has already passed.
The start time can be programmed in the EMACTARGSEC and EMACTARGNANO registers. The
TRGTBUSY bit in the EMACTARGNANO register indicates when the value is synchronized to the PTP
clock domain. When this bit is clear, a new start time can be programmed, even before the earlier start
time has elapsed. The start or stop time should be programmed with advanced system time to ensure
proper EN0PPS signal output. If the application programs a start or stop time that has already elapsed,
then the MAC sets an error status bit indicating the programming error. If enabled, the MAC also sets the
Target Time Reached interrupt event. The application can cancel the start or stop request only if the
corresponding start or stop time has not elapsed. If the time has elapsed, the cancel command has no
effect.
For a flexible EN0PPS output, the EMACPPS0INTVL and EMACPPS0WIDTH registers can be configured.
The PPS0WIDTH and PPS0INT fields are programmed in terms of granularity of system time, that is,
number of the units of subsecond increment value. For example, to have a EN0PPS pulse width of 80 ns
and interval of 120ns, with the PTP reference clock of 25MHz, you should 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.
15.3.6.5.5 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.
15.3.6.5.6 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:
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Enable snapshot for all frames
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Enable snapshot for IEEE 1588 version 2 or version 1 timestamp
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Enable snapshot for PTP frames transmitted directly over Ethernet or UDP-IP-Ethernet
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Enable timestamp snapshot for the received frame for IPv4 or IPv6
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Enable timestamp snapshot only for EVENT messages (SYNC, DELAY_REQ, PDELAY_REQ, or
PDELAY_RESP)
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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.
15.3.7 Frame Filtering
The following types of filtering are available for receive frames:
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Source Address (SA) or Destination Address (DA) filtering
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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.