Hardware Spec

Introduction to AXI bus

How AXI bus works

The AXI bus is a high-performance, high-bandwidth, and scalable on-chip interconnect bus. It is used to connect different components of a system-on-a-chip (SoC), such as the CPU, memory, and peripherals.

The AXI bus consists of four main components:

  • AXI masters: These are the components that initiate data transfers on the AXI bus. The CPU, DMA controller, and graphics controller are examples of AXI masters.
  • AXI slaves: These are the components that receive data transfers on the AXI bus. Memory and peripherals are examples of AXI slaves.
  • AXI interconnect: This is the physical medium that connects the AXI masters and slaves.
  • AXI protocol: This is the set of rules that govern how data is transferred on the AXI bus.

The AXI bus works by using a four-phase handshake protocol. In each phase, the AXI master and slave exchange control signals to agree on the parameters of the data transfer, such as the address, data width, and data type. Once the parameters have been agreed upon, the AXI master transfers the data to the AXI slave.

The AXI bus is a very flexible and efficient interconnect bus. It can be used to connect a wide variety of components in a SoC. It is also scalable, so it can be used to build systems with a wide range of performance requirements.

How AXI devices work

AXI devices are devices that comply with the AXI protocol. This means that they can communicate with other AXI devices on the AXI bus.

AXI devices are typically implemented as hardware blocks. However, they can also be implemented in software.

When an AXI device is implemented in hardware, it is typically connected to the AXI bus using a dedicated physical interface. This interface allows the device to send and receive data on the AXI bus.

When an AXI device is implemented in software, it is typically implemented as a driver. The driver is responsible for communicating with the device on the AXI bus.

How AXI bus communicates with other buses

The AXI bus can communicate with other buses using a variety of methods. One common method is to use a bridge. A bridge is a device that connects two different buses.

Another common method is to use a switch. A switch is a device that connects multiple buses together.

The AXI bus can also communicate with other buses using a direct connection. This is typically done by connecting the two buses using a physical interface.

Compare AXI bus with others

The AXI bus is a relatively new bus standard. It has been designed to overcome some of the limitations of older bus standards, such as the ARMAMBA bus and the AHB bus.

Some of the advantages of the AXI bus include:

  • It is a high-performance bus.
  • It is a scalable bus.
  • It is a flexible bus.
  • It is a well-defined bus.

Some of the disadvantages of the AXI bus include:

  • It is a complex bus.
  • It is a power-hungry bus.
  • It is a relatively new bus, so there is not as much support for it as there is for older bus standards.

Overall, the AXI bus is a high-performance, scalable, and flexible bus standard. It is a good choice for systems that require high performance and flexibility.

AMBA

The AXI bus is included in AMBA (Advanced Microcontroller Bus Architecture). AMBA is a set of standards for on-chip communication between different components of a system-on-a-chip (SoC). The AXI bus is one of the most popular AMBA standards. It is a high-performance, scalable, and flexible bus that can be used to connect a wide variety of components in a SoC.

Here are some of the other AMBA standards:

  • AHB (Advanced High-performance Bus): A high-performance bus that is used to connect high-speed components in a SoC.
  • APB (Advanced Peripheral Bus): A low-power bus that is used to connect low-speed components in a SoC.
  • ACE (Advanced Coherency Extensions): A set of extensions to the AXI bus that provide system-wide coherency for cache-coherent systems.
  • CHI (CoreSight interconnect): A high-speed interconnect that is used to connect the different components of the CoreSight debug and trace system.

AMBA standards are widely used in SoC designs. They provide a standardized way to connect different components in a SoC, which makes it easier to design, develop, and debug SoCs.