Errors In Messages - Intel IXP45X Developer's Manual

Time Synchronization Hardware Assist (TSYNC)—Intel
Line of Network Processors
Below is a description of the messages and how they are detected and utilized in the
TSync block. For simplification, the description will reference a single channel and leave
off the numeric descriptors as defined in the logic and register definitions.
Sync Message
19.3.10.1
The master channel multicasts a Sync message periodically over the network at 1-, 2-,
8-, 16-, or 64-second intervals. A Sync message is defined as a value of 0x00 in byte
74 of the Ethernet frame after the start of frame delimiter.
If the channel is a master, the Time Sync logic will monitor the MII signals and detect
when the master channel has transmitted a Sync message. When the SFD is detected
and the XMIT_Snapshot is not locked out, the message is time stamped and the
current system time is captured in the XMIT_Snapshot register.If the channel is a slave,
Sync messages will be received (not transmitted). When the SFD is detected and the
RECV_Snapshot is not locked out, the message is time stamped and the current system
time is captured in the RECV_Snapshot register.When the snapshot of system time
related to the Sync message has occurred, an indication asserts in the
TS_Channel_Event register and remains set until firmware explicitly writes a '1' back to
that bit. Until the Sync message snapshot indication is cleared, no further Sync
messages will be time stamped. Locking can be inhibited by setting the
TS_Channel_Control register appropriately.
Delay_Req Message
19.3.10.2
Slave channels transmit a Delay_Req message to the master in response to receiving a
Sync message. A Delay_Req message is defined as a value of 0x01 in byte 74 of the
Ethernet frame after the start of frame delimiter.
If the channel is a master, the Time Sync logic will monitor the MII signals and detect
when the master channel has received a Delay_Req message. When the SFD is
detected and the RECV_Snapshot is not locked out, the message is time stamped and
the current system time is captured in the RECV_Snapshot register.If the channel is a
slave, Delay_Req messages will be transmitted (not received). When the SFD is
detected and the XMIT_Snapshot is not locked out, the message is time stamped and
the current system time is captured in the XMIT_Snapshot register.When the snapshot
of system time related to the Delay_Req message has occurred, an indication asserts in
the TS_Channel_Event register and remains set until firmware explicitly writes a '1'
back to that bit. Until the Delay_Req message snapshot indication is cleared, no further
Delay_Req messages will be time stamped. This is important to note since multiple
slave channels may try to send Delay_Req messages simultaneously. Locking can be
inhibited by setting the TS_Channel_Control register appropriately.
19.3.10.3

Errors in Messages

The TSync logic will ignore 1588 time-sync messages that are not properly formatted
as described above. CRC errors or other errors detected by the MAC or higher levels of
the protocol will cause firmware to delete the message and any time snapshots
incorrectly captured by the TSync logic to be ignored.
Note: On the IXP45X/IXP46X network processors, the TSync logic does not check if properly
formatted messages have PHY errors.
August 2006
Order Number: 306262-004US
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IXP45X and Intel IXP46X Product
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Intel IXP45X and Intel IXP46X Product Line of Network Processors
Developer's Manual
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