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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
877 of 1441
NXP Semiconductors
UM10503
Chapter 28: LPC43xx/LPC43Sxx Ethernet
28.7.5.6 Receive path functions
When you select the advanced timestamp feature, the MAC processes the received
frames to identify valid PTP frames. You can control the snapshot of the time, to be sent to
the application, by using the following options of the timestamp control register
(
•
When you select the advanced timestamp feature, the MAC processes the received
frames to identify valid PTP frames. You can control the snapshot of the time, to be
sent to the application, by using the following options of the Timestamp Control
Register.
•
When you select the advanced timestamp feature, the MAC processes the received
frames to identify valid PTP frames. You can control the snapshot of the time, to be
sent to the application, by using the following options of Register 448 (Timestamp
Control Register).
•
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 for EVENT messages (SYNC, DELAY_REQ,
PDELAY_REQ or PDELAY_RESP) only.
•
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.
Remark:
The ethernet controller also supports PTP messages over VLAN frames.
The MAC provides the time stamp, along with EOF. An additional signal validates the
presence of timestamp for the receive frame.
The MTL provides the time stamp on the data bus after the EOF data has been
transferred. An additional signal validates the timestamp. This signal is asserted to
indicate the availability of timestamp. Once the timestamp is transferred, the MTL sends
the receive status to the application. In 32-bit datawidth mode, the MTL provides the
additional status related to the timestamp on the data bus after the normal status is read.
The additional status is provided only when the bit 0 of the normal status is set and is
validated.
The DMA returns the time stamp to the software inside the corresponding Transmit and
Receive Descriptor. The advanced timestamp feature is supported only with the 32-bytes
long Alternate (Enhanced) descriptor. The extended status, containing the timestamp
message status and the IPC status, is written in descriptor RDES4 and the snapshot of
the timestamp is written in descriptors RDES6 and RDES7. For detailed information about
descriptors, see
.
28.7.6 DMA controller description
The DMA has independent Transmit and Receive engines and a CSR space. The
Transmit engine transfers data from system memory to the device port (MTL), while the
Receive engine transfers data from the device port to the system memory. The controller
uses descriptors to efficiently move data from source to destination with minimal Host
CPU intervention. The DMA is designed for packet-oriented data transfers such as frames