19.3.3.1.1 Undefined Length Burst Arbitration

In order to prevent Client handling during undefined length bursts, the user can trigger the re-arbitration before the end of the incremental bursts. The re-arbitration period can be selected from the following Undefined Length Burst Type (ULBT) possibilities:

  1. Unlimited: no predetermined end of burst is generated. This value enables 1-Kbyte burst lengths.
  2. 1-beat bursts: predetermined end of burst is generated at each single transfer during the INCR transfer.
  3. 4-beat bursts: predetermined end of burst is generated at the end of each 4-beat boundary during INCR transfer.
  4. 8-beat bursts: predetermined end of burst is generated at the end of each 8-beat boundary during INCR transfer.
  5. 16-beat bursts: predetermined end of burst is generated at the end of each 16-beat boundary during INCR transfer.
  6. 32-beat bursts: predetermined end of burst is generated at the end of each 32-beat boundary during INCR transfer.
  7. 64-beat bursts: predetermined end of burst is generated at the end of each 64-beat boundary during INCR transfer.
  8. 128-beat bursts: predetermined end of burst is generated at the end of each 128-beat boundary during INCR transfer.

The use of undefined length16-beat bursts, or less, is discouraged since this decreases the overall bus bandwidth due to arbitration and Client latencies at each first access of a burst.

If the Host does not permanently and continuously request the same Client or has an intrinsically limited average throughput, the ULBT should be left at its default unlimited value, knowing that the AHB specification natively limits all word bursts to 256 beats and double-word bursts to 128 beats because of its 1-Kbyte address boundaries.

Unless duly needed, the ULBT should be left at its default value of 0 for power saving.

This selection is made through the ULBT field of the Host Configuration Registers (MATRIX_MCFG).