Achronix Speedster22i Interlaken - Manual (Page 26)

1, the value of tx_mtyin[2:0] is ignored as if it was 000. The other bits of tx_mtyin are used as
usual.
Data can be safely written, i.e. tx_enain asserted, whenever tx_rdyout is asserted. After tx_rdyout
is negated, additional 16 writes, using tx_enain, can be safely performed provided tx_ovfout is
never asserted. Once tx_rdyout is asserted again, additional data can be written. If, at any time,
the back-pressure mechanism is violated, the tx_ovfout is asserted to indicate the violation.
Data Formatting
Interlaken segments packets into bursts as described in the Interlaken Protocol Definition rev 1.2 .
A burst is a sequence Data Word between two Control Words. The size of the bursts generated by
the IIPC is controlled by two factors:
1. Parameters ctl_tx_burstmax and ctl_tx_burstshort programmed in registers
2. How the user write packets into the TX
The IIPC operates in one of two modes, depending on how the user writes data into the TX:
1. Packet Mode
2. Segment Mode
Packet Mode
Packet mode simply means that a packet with a certain channel number is written in its entirety
without interruption by a packet for a different channel. The first data written for a packet begins
with tx_sopin asserted and the final write operation has tx_eopin asserted.
Unless tx_bctlin is asserted (see the
Use of tx_bctlin
section) the size of the bursts (i.e. the
number of Data Word between Control Words) will be ctl_tx_burstmax except for the last burst of
a packet which will be between ctl_tx_burstshortand ctl_tx_burstmax
Segment Mode
Segment mode simply means that packets with different channel addresses/identifiers may be
interleaved.
User’s tasks:
•
Once tx_sopin has been asserted for a channel, do not assert again for that channel until a
corresponding tx_eopin for that channel has been written.
• Unless tx_eopin is asserted, provide valid data to the full width of the data bus (tx_datain) as
discussed in the
TX LBUS Interface
section above.
The size of the bursts generated in Segment mode is governed by the tx_bctlin input (see the
Use
of tx_bctlin
section), ctl_tx_burstshort, ctl_tx_burstmax, and the changing of the channel ID of
packets.
User’s tasks:
• It is strongly recommended to implement the Optional Scheduling Enhancement as
described in section 5.3.2.1.1 of the Interlaken Protocol Definition rev1.2 document to
maximize throughput.
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