What is Mmio in PCIe?

Memory-mapped I/O (MMIO) and port-mapped I/O (PMIO) are two complementary methods of performing input/output (I/O) between the central processing unit (CPU) and peripheral devices in a computer. The memory and registers of the I/O devices are mapped to (associated with) address values.

What is base address register in PCIe?

A Base Address Register (BAR) is used to: – specify how much memory a device wants to be mapped into main memory, and. – after device enumeration, it holds the (base) address, where the mapped memory block begins. A device can have up to six 32-bit BARs or combine two BARs to a 64-bit BAR.

What is the base address register?

The base address register is a pointer to a byte in memory, and the offset specifies a number of bytes. Immediate means the address is calculated using the base address register and a 12-bit offset encoded in the instruction.

What is PCIe enumeration?

PCIe enumeration is a process of detecting devices connected to its host. Generally there is only one host that is connected to the CPU which is further connected to a PCIe Switch which connects different End Points to the host as shown in the picture below.

How does MMIO work?

The MMIO write operation transmits the data and a portion of the address to the device, and the device uses both quantities to determine how it should change its state. MMIO reads are used for two-way communication, causing the device to return a value based on its current state.

What is MMIO in Linux?

Memory-mapped I/O (MMIO) and port-mapped I/O (PMIO) are two complementary methods of performing input/output(I/O) between CPU and peripheral devices in a computer. Linux provides the pcimem utility to allow reading from and writing to MMIO addresses.

What is PCI base address?

The PCI configuration space consists of up to six 32-bit base address registers for each device. These registers provide both size and data type information. System firmware assigns base addresses in the PCI address domain to these registers.

What is base register?

A Base register is a Statistical register of great importance for the whole register system of a statistical office. SOURCES: Primary source: CODED-Administrative register.

How is the base effective register address determined?

Base register addressing mode:Base register addressing mode is used to implement inter segment transfer of control.In this mode effective address is obtained by adding base register value to address field value. EA= Base register + Address field value. PC= Base register + Relative value.

What is MMIO write?

MMIO writes are used for one-way communication, causing the device to change its state, as shown in the diagram on the right. The MMIO write operation transmits the data and a portion of the address to the device, and the device uses both quantities to determine how it should change its state.