| 摘要 |
A bus has a local section (10a,b) and a shared section (11a,b). An arbiter circuit (16) issues an arbited grant (25) to access the shared section (11a,b) in response to a request (22) to perform a bus access transaction. A bus station (12) has a request output (17a) for issuing the request to the arbiter (16), the bus station (12) having a grant input (19c) arranged to receive a local grant (24) in response to the request (22), independently of the arbited grant (25). The bus station (12) is arranged to start the transaction, applying an address to the local section (10a,b) in response to the local grant (24) in a bus cycle following the local grant (24). A bridge circuit (16) provides a coupling between the local section (10a,b) and shared section (11a,b). The bridge station receives the arbited grant (25) and enables the coupling to pass the address to the shared section (11a,b) in said bus cycle conditional on the arbited grant (25). The bridge circuit (16) signals the station (12) to disable progress of the transaction when it detects that the address addresses a bus unit (14b,c) on the shared bus (11a,b) and no arbited grant (25) is received in response to the request (22) before said bus cycle.
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