求问：PCI总线架构下如何实现设备的配置

shark21

PCI总线架构下如何实现设备的配置：PCI总线上的配置访问分为两种：TYPE0访问和TYPE1访问。比如我的设计是bus0（主）上有一个设备slot0和一个pci－pci 桥。这个pci－pci 桥下挂了4个slot（slot1、2、3、4），总线为bus1（从）。很清楚的是如果访问slot0，则用TYPE0访问（slot0的idsel接bus0的p_AD【31】）；如果访问slot1，则用TYPE1访问，如果bus number 吻合的话，就在bridge的等级上对slot1进行TYPE0访问（TYPE1的device number【15：11】为01110B,对应slot1的idsel接bus1的s_AD【30】）。
上述讲的是downstream。我的问题是桥芯片上的IDSEL引脚应该接什么，？？
求求各位了

jingli888ca

Hello,
This is simple, you can simply connect the AD lines (high bits, 31, 30, 29, 28) to slot 1, 2, 3, and 4. When the PCI-PCI bridge pass the type 1 cycles (configuration), it will poll its AD line in turns to find out if there is a slot attached to it. If the slot has a device and the device reponds with a DEVSEL# assertion, it will continue the configuration; otherwise, it will skip this one, and try next AD line.
Hope this clarify your question.