Use of TX_BCTLIN - 2.4 English - PG169

The tx_bctlin<N> input operates in a similar manner to tx_sopin<N> or a change in tx_chanin<N>; they cause a Burst Control Word to be injected into the data stream before the data on segment <N>.

The purpose of the tx_bctlin<N> 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, Revision 1.2, October 7, 2008.

The Integrated Interlaken IP core strictly observes the programmed values for CTL_TX_BURSTMAX and CTL_TX_BURSTSHORT and injects Burst and Idle Control Words where required. Consequently, the Integrated Interlaken IP core can inject Idle Control Words that otherwise would not be required, which results in reducing the effective bandwidth.

For example, assume the CTL_TX_BURSTMAX is set to 256 bytes and CTL_TX_BURSTSHORT is set to 64 bytes. A packet of 264 bytes written into the Integrated Interlaken IP core, without the use of tx_bctlin<N>, is followed by three undesirable Idle Control Words that are required to meet the CTL_TX_BURSTSHORT parameter. Specifically:

1. One Burst Control Word (with Start of Packet) is sent.
2. 32 Data Words are sent.
3. One Burst Control Word (without Start of Packet) is sent.
4. One Data Word is sent.
5. Seven Idle Control Words are sent (to satisfy BurstShort) for a total of 42 Words.

If the corresponding tx_bctlin<N> signal is asserted after 128 bytes are sent, the following occurs:

1. One Burst Control Word (with Start of Packet) is sent.
2. 16 Data Words are sent.
3. One Burst Control Word (without Start of Packet) is sent.
4. 17 Data Words are sent.
5. Zero Idle Control Words is sent for a total of 35 Words.

Ensure that all rules that govern Interlaken bursts, as defined in the Interlaken Protocol Definition, Revision 1.2, October 7, 2008, are followed when using Integrated Interlaken IP core signals. In particular, you must ensure that each burst on each channel which is not EOP or EOP-1 is equal to BurstMax.