1. Decoder
The decoder manages all transfers on the ASB bus. Each bus transfer requires three components to act:
- A bus master to start the transfer.
- The decoder to control the operation of the transfer.
- A bus slave to accept a write transfer or control a read transfer.
- BTRAN is used to determine how the transfer should proceed, whether a slave should be selected, if and in which state slave responses (BWAIT, BERROR and BLAST) should be driven. The high order bits of BA are used to generate the corresponding slave select line (DSEL).[21]
2. Bus Master
This initiates a read or write transfer by driving BTRAN[1:0] (transfer type) and BA[31:0] (AMBA address bus) and control signals. This component drives BD[31:0] (bidirectional system data bus) for a write transfer.