Achronix Speedster22i Interlaken - Manual (Page 27)

• It also strongly recommended that the changing of channels be such that the number of
bytes between Control Words, whether forced (via tx_bctlin) or implied, be a multiple of
ctl_tx_burstmax. Except for the last burst of a packet, no burst should ever be less than
ctl_tx_burstshort.
Use of tx_bctlin
The tx_bctlin input operates in a similar manner to tx_sopin: both signals cause a Burst Control
Word to be injected into the data stream.
The purpose of the tx_bctlin input is to permit the forcing of Burst Control Words that otherwise
would not be transmitted. This is a necessary function for the creation of an external scheduler
that implements the Optional Scheduling Enhancement described in section 5.3.2.1.1 of the
Interlaken Protocol Definition rev1.2.
The IIPC strictly observes the programmed values for ctl_tx_burstmax and ctl_tx_burstshort and
injects Burst and Idle Control Words where required. Consequently, the IIPC may inject Idle
Control Words, that otherwise would not be required and thereby reduce effective bandwidth.
User’s task:
• Ensure that all rules governing Interlaken bursts, as defined in the Interlaken Protocol
Definition Revision 1.2, are followed when using tx_bctlin.
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