What are PCIe Configuration Registers?

The PCIe interface is a widely used technology today, but it is a bit difficult to understand from the PCIe Specification alone, so this column will explain topics extracted from the specification.

The basic Registers of the PCIe Device are located in an area called Configuration Registers.

There are various Registers in this Configuration Register, but here we will explain the Configuration Space Header.

The Configuration Space Header is divided into Type0 and Type1, and consists of a common part and a Type individual part. Type 0 Configuration Space Hader is used for Endpoint Device, Type 1 Configuration Space Header is used for Root Port and Upstream Port/Downstream Port of PCIe Switch.

The format is shown below. Please check the PCIe standard for details.

* The Type Specific Field in the above format configures different Registers for Type 0 and Type 1.

Format difference

The following describes the differences in format between the Type 0 Configuration Space Register and the Type 1 Configuration Space Register.

You can access the Type 0 Configuration Space Header using Type 0 Configuration Read/Write and the Type 1 Configuration Space Header using Type 1 Configuration Read/Write.

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