Dual-Simplex
The PCI Express serial bus is a dual-simplex bus (see Figure A-3 on page 965), unlike the parallel-based PCI bus where the start and end of a transfer can be seen on the same bus as shown in Figure A-1 on page 962.
Figure A-3. PCI Express Dual-Simplex Bus
This architecture requires the requester to transmit a “Request” for data transfer on one transmit pair, while it receives the “Completion” response on the receive signal pair. Considering that the response time can widely vary, developers need to be able to set the analyzer to filter the received and the transmitted data independent of each other.
Also the agents on the two ends ...
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