| 摘要 |
A bus has a local section ( 10 a,b) and a shared section ( 11 a,b). An arbiter circuit ( 16 ) issues an arbited grant ( 25 ) to access the shared section ( 11 a,b) in response to a request ( 22 ) to perform a bus access transaction. A bus station ( 12 ) has a request output ( 17 a) for issuing the request to the arbiter ( 16 ), the bus station ( 12 ) having a grant input ( 19 c) 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 ( 10 a,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 ( 10 a,b) and shared section ( 11 a,b). The bridge station receives the arbited grant ( 25 ) and enables the coupling to pass the address to the shared section ( 11 a,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 ( 14 b,c) on the shared bus ( 11 a,b) and no arbited grant ( 25 ) is received in response to the request ( 22 ) before said bus cycle.
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