Altera POS-PHY Level 4 IP Core - Manual (Page 85)

Chapter 5: Functional Description—Transmitter 5–15
Error Flagging and Handling
December 2014 Altera Corporation POS-PHY Level 4 IP Core User Guide
If a SOP is detected during an open packet, then err_aN_meopN is asserted. The packet
is terminated with an EOP-Abort, and data is ignored for that port until an EOP is
received.
If a MTY is non-zero when a missing EOP is not asserted, then err_aN_meopN is
asserted. The packet is terminated with an EOP-Abort, and data is ignored for that
port until a SOP is received.
The Atlantic FIFO buffer error checker block also handles overflows. If an overflow
occurs, the error checker block rejects all inputs until the buffer is drained of all of its
data (err_aN_fifo_oflwN is asserted), however existing internal calendar values are
left untouched. Any open packets are truncated with the EOP and ERR signals (this
leads to EOP abort on the SPI-4.2 bus). If the last successful write immediately before
the overflow was an EOP, then truncation is unnecessary. All writes to the buffer are
discarded and ignored. The Atlantic write aN_atxdav signal is forced low (to indicate
to the user logic to stop writing) during the flushing operation. The buffer is fully
flushed out (due to the assurance that no EOP is present in the buffer). Flushing is
accomplished by the transmitter IP core as it continues to read data from the buffer.
Complete packets already written to the buffer before the overflow occurred are not
corrupted and are safely transmitted. Once the buffer is empty, the aN_atxdav signal is
released and the err_aN_fifo_oflwN flag is deasserted low. Writes to the buffer are
ignored until a SOP is received, for each port that had an open packet during the
overflow. Refer to
Figure 5–11 on page 5–16 .
Missing SOP
Figure 5–7 and Figure 5–8 show missing SOP.
Figure 5–7. Atlantic Interface with Missing SOP
Figure 5–8. Output from Atlantic Error Checker Block (Corrected MSOP)
Missing SOP
aN_atxeop
aN_atxerr
aN_atxtclk
aN_atxena
aN_atxsop
err_ry_msopN
aN_atxeop
aN_atxerr
aN_atxtclk
aN_atxena
aN_atxsop