SPRUIL1D May 2019 – December 2024 DRA829J , DRA829J-Q1 , DRA829V , DRA829V-Q1 , TDA4VM , TDA4VM-Q1
The TBU module reads transactions from CBASS, performs permission checks and address translations from virtual addresses then returns translated physical address transactions to CBASS. The architectural 2-stage translation and intermediate physical addresses (IPA) and the are not visible or exported to the rest of the system.
TBU is segregated from PAT and PVU paths to avoid short-term interference due to TBU blocking conditions on real-time traffic.
Figure 8-14 TBU Functional DiagramOn the path through the TBU, egress logic from CBASS converts the transactions to the format expected by the TBU. Internally, TBU provides payload-wide buffering and arbitration to support reordering as a result of TBU misses. Additionally, per Arm documentation, the TBU contains a bypass path that copies the input transaction to the output without translation or permission checking. Once the TBU has completed operating on a transaction, CBASS ingress logic converts the TBU output to format expected by CBASS and the transaction is transported to its final destination.