PCI协议笔记note.docVIP

PCI Speci rev2.3 FRAME# is driven by the master to indicate the beginning and end of a transaction. IRDY# is driven by the master to indicate that it is ready to transfer data. TRDY# is driven by the target to indicate that it is ready to transfer data. IDSEL in Initialization Device Select is used as a chip select during configuration read and write transactions. STOP# s/t/s Stop indicates the current target is requesting the master to stop the current transaction. In all cases, data is only transferred when IRDY# and TRDY# are both asserted on the same rising clock edge. 只有当IRDY# and TRDY#都有效时，数据才能传输。 3.2.2. Addressing PCI targets (except host bus bridges) are required to implement Base Address register(s) to request a range of addresses which can be used to provide access to internal registers or functions (refer to Chapter 6 for more details). The configuration software uses the Base Address register to determine how much space a device requires in a given address space and then assigns (if possible) where in that space the device will reside. BAR确定一个设备需要多少空间。 A device may map its internal register into both Memory Space and optionally I/O Space by using two Base Address registers, one for I/O and the other for Memory. When a transaction is initiated on the interface, each potential target compares the address with its Base Address register(s) to determine if it is the target of the current transaction. If it is the target, the device asserts DEVSEL# to claim the access. For more details about DEVSEL# generation, refer to Section 3.2.2.3.2. How a target completes address decode in each address space is discussed in the following sections. 当一个交易初始后，每个潜在设备将自己的BAR与总线上的地址比较，来确定自己是不是当前交易的目标。 3.2.2.1. I/O Space Decoding In the I/O Address Space, all 32 AD lines are used to provide a full byte address. The master that initiates an I/O transaction is required to ensure that AD[1::0] indicate the least significant valid byte for the transaction. The byte enables indicate