PCIe-7.3.4 PCI Special Cycles

*PCI Special Cycles (see the [PCI] for details) are not directly supported by PCI Express. PCI Special Cycles may be directed to PCI bus segments behind PCI Express-PCI Bridges using Type 1 configuration cycles as described in the [PCI].*逐句解释PCI Special Cycles (see the [PCI] for details) are not directly supported by PCI Express.解释：PCI Special Cycles是传统PCI总线中定义的一种特殊总线周期（Bus Cycle）。它用于向总线上的所有设备广播一种特殊消息，例如：SHUTDOWN（关机）HALT（停机）FLUSH（刷新缓存）或者厂商自定义的同步消息。在PCI协议中，Special Cycle是一种