Lately we have seen a trend of serial data transfers in place of parallel data transfer for improved performance and data integrity. One example of this is the migration from PCI/PCI-X to PCI Express. A serial interface between two devices results in fewer number of pins per device package. This not only results in reduced chip and board design cost but also reduces board design complexity. As serial links can be clocked considerably faster than parallel links, they would be highly scalable in terms of performance.
However, to accelerate verification of PCI Express based sub-systems and to accelerate the PCI Express endpoint development time , PIPE (PHY Interface for the PCI Express Architecture) was defined by Intel and was published for industry review in 2002. PIPE is a standard interface defined between a PHY sub-layer which handles the lower levels of serial signaling and the Media Access Layer (MAC)
which handles addressing/access control mechanisms. The following diagram illustrates the role PIPE plays in partitioning the PHY layer for PCI Express.
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