- Hardware timestamping at full Ethernet
line rate on both transmit and receive paths. Timestamp accuracy is better than ±10
ns under all operating conditions.
- 1-step and 2-step support for Time of
Day (ToD) timestamps (IEEE1588-2008 format consisting of a 48-bit seconds field and
a 32-bit nanoseconds field).
- On receive, all frames are timestamped
with a captured 80-bit ToD timestamp. The full 80-bit timestamp is provided to the
client logic out of band using the ports defined in IEEE 1588 Received Timestamp Ports. In addition, an optional 64-bit timestamp can be provided in line with the
received frame. This 64-bit timestamp consists of the lower 32 bits from the 1588
timers seconds field, plus all 32 bits of the nanoseconds field. For the Correction
Field format, the full 64-bit timestamp is provided to the client logic out of band
using ports defined in Table 2. In
addition, the 64-bit timestamp can optionally be provided in line with the received
frame. All PTP frame types are supported on receive.
- On transmit:
- A command field is provided by
the client to the TEMAC either in line with the frame sent for transmission,
or in parallel with the frame sent for transmission. This indicates, on a
frame-by-frame basis, the 1588 function to be performed (no-operation,
1-step or 2-step) and also indicates, for 1-step frames, whether there is a
UDP checksum field that requires updating.
- For 1-step and 2-step operation, the full 80-bit captured
ToD timestamp is returned to the client logic using the additional ports
defined in IEEE 1588 Transmit Timestamp Ports.
- For 1-step operation, the full 80-bit ToD captured timestamp
is inserted into the frame.
- For 1-step UDP frame types, the UDP checksum is updated in
accordance with IETF RFC 1624. (In order for this update function to work
correctly, the original checksum value for the frame sent for transmission
should be calculated using a zero value for the timestamp data).
- For all 1-step frames, the Ethernet Frame Check Sequence
(FCS) field is calculated after all frame modifications have been
completed.
- Supported 1588 PTP frame types are:
- For transmit 1-step:
- Raw Ethernet frames
- UDP IPv4 frames
- UDP IPv6 frames
- For transmit 2-step, all Precise Timing Protocol (PTP) frame
formats can be supported.
- For receive, all PTP frame formats can be supported.