Datasheet

DP83640

www.ti.com

SNOSAY8E –SEPTEMBER 2007–REVISED APRIL 2013

2.3.2 PACKET TIMESTAMPS

2.3.2.1 IEEE 1588 Transmit Packet Parser and Timestamp

The IEEE 1588 transmit parser monitors transmit packet data to detect IEEE 1588 Version 1 and Version

2 Event messages. The transmit parser can detect PTP Event messages transported directly in Layer2

Ethernet packets as well as in UDP/IPv4 and UDP/IPv6 packets. Upon detection of a PTP Event

Message, the device will capture the transmit timestamp and provide it to software.

Since software knows the order of packet transmission, only the timestamp is recorded (there is no need

to record sequence number or other information). The device can buffer four timestamps.

If enabled, an interrupt may be generated upon a Transmit Timestamp Ready.

2.3.2.1.1 One-Step Operation

In some cases, the transmitter can be set to operate in a One-Step mode. For Sync Messages, a One-

Step device can automatically insert timestamp information in the outgoing packet. This eliminates the

need for software to read the timestamp and send a follow up message.

2.3.2.2 IEEE 1588 Receive Packet Parser and Timestamp

The IEEE 1588 receive parser monitors receive packet data to detect IEEE 1588 Version 1 and Version 2

Event messages. The receive parser can detect PTP Event messages transported directly in Ethernet

packets as well as in UDP/IPv4 and UDP/IPv6 packets. Upon detection of a PTP Event message, the

device will capture the receive timestamp and provide the timestamp value to software. In addition to the

timestamp, the device will record the 16-bit SequenceId, the 4-bit messageType field, and generate a 12-

bit hash value for octets 20-29 of the PTP event message. The device can buffer four timestamps.

An interrupt will be generated, if enabled, upon a Receive Timestamp Ready.

2.3.2.2.1 Receive Timestamp Insertion

The DP83640 can deliver the timestamp to software by inserting the timestamp in the received packet.

This allows for a simple method to deliver the packet to software without having to match the timestamp to

the correct packet. This also eliminates the need to read the receive timestamp through the Serial

Management Interface.

2.3.2.3 NTP Packet Timestamp

The DP83640 may be programmed to timestamp NTP packets instead of PTP packets. This operation is

enabled by setting the NTP_TS_EN control in the PTP_TXCFG0 register. When configured for NTP

timestamps, the DP83640 will timestamp packets with the NTP UDP port number rather than the PTP port

number (note that the device cannot be configured to timestamp both PTP and NTP packets). One-Step

operation is not supported for NTP timestamps, so transmit timestamps cannot be inserted directly into

outgoing NTP packets. Timestamp insertion is available for receive timestamps but must use a single,

fixed location.

2.3.3 EVENT TRIGGERING AND TIMESTAMPING

2.3.3.1 IEEE 1588 Event Triggering

The DP83640 is capable of being programmed to generate a trigger signal on an output pin based on the

IEEE 1588 time value. Each trigger can be programmed to generate a one-time rising or falling edge, a

single pulse of programmable width, or a periodic signal.

For each trigger, the microcontroller specifies the desired GPIO and time that the activity is to occur. The

trigger is generated when the internal IEEE 1588 clock matches the desired activation time.

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