Difference between AHB and APB

Difference between AHB and APB

AHB is an acronym for Advanced High-performing Bus, while APB is an acronym for Advanced Peripheral Bus. They all come from Advanced Microprocessors Bus Architecture. Even though they are parts of AMBA, and are of chip Bus operation, they have unique features that differentiate the former from the latter.

AHB uses whole duplex parallel communications, whereas APB uses huge memory -I/O accessed. AHB is capable of bursts, waits, and errors. The ADH that’s pipelined connects memories.


Their differences stem first from their meaning. When you look at AHB, it stands for Advanced High Performing Bus, whereas APB stands for Advanced Peripheral Bus. Advanced High performing Bus differs from Advanced Peripheral Bus if you look at their uses. For instance, APB is straightforward compared to AHB.

Another feature is that there are vacancies in AHB than APB. Advanced High performing Bus was first proposed by ARM Limited as AMBAs second design version publication. It’s basically a transactional entailing addressing phase, then a data phase. It uses MUX that limits the accessibility of a particular device. Ensuring that one Bus master uses it at a time.

On the other hand, Advanced Peripheral Bus is simple and relatively low. A reduced peripheral version is used for low electronics. There are parts in this Bus that will dangle off on a network interface in any particular setup. They include DMA sensors, On-chip storage, SoC processors, and storage drivers. It’s also responsible for the raised links of a processor.

What is AHB?

While creating Advanced Microprocessor Bus Architecture second version, AHB was installed to create a superior designs. Apart from AHB, other features were added to AMBA 2.0. They included split operations, one edge functioning, wider data bus setup, and one cycle bus master changeover.

The vassals, lords, and AHB have several parts from the exterior. They include, writing multiplexer, location and control expander, decoder, arbitrator, and scan multiplexer. You will also notice other features on the AMBA 2.0 that serve various functions. For instance, the addressing signal (HADDR), the writing data bus (HWDATA), the reading data bus (HRDATA). The location will pick up a slave, and then the writing data bus will transmit information from the owner to the slave; after that, the reading data bus will transfer data from servants to masters.

A master will create a message to the arbitrator before taking ownership of the data bus. The arbitrator works in such a way that it will give access to a master that has prime importance before the rest of them. It’s important to note that AMBA has not incorporated this feature; therefore will vary from design to design.

The route a data takes, its breath, and type of data flowing are outlined by the multitude of data amplifications. The master’s message IP will internalize the message and turn it into slave impulses by the AHB decoder. It will then receive a signal in HRESP form from the slave, and the data transmission that’s between the owner and SERF commences.

What is APB?

Advanced Peripheral Bus is just a simple Bus and doesn’t support breaking. It has two phases in every contract, and they include an addressing cycle-setup phase and a data cycle-enable phase. APH uses a single Clock (PCLK). The bus will bring out the (PSEL) and (PWRITE) during its configuration and is designed in such a way that their destination is at (PADDR) addressing bus.

It works to put the PENBLE upwards and secures the writing data bus (PWDATA) and reading data bus (PRDATA) in the enable condition. After the ENABLE indication on the clock, the PENABLE gets de-asserted.

The AMBA team came together it to comprise of APH. Time limiters halt drivers, I/O ports, UARTs, and various other accessories are used. The team ensures to minimize to optimize low power usage and interface complexity. It doesn’t use pipelines and uses two rounds- access and setup cycles in transmission.

Low peripheral are rightly depicted in AMBA APB. It has to turn to a low energy consumption and complex interface for it to work. The good about this bus is that it can be used with any iteration of a unit bus.

Difference between AHB and APB

  • AHB stands for Advanced High performing Bus while APB stands for Advanced Peripheral Bus.
  • AHB will always communicate in duplex parallel mode, whereas APB will utilize its -I/O memory for communication
  • When you look at two buses, you’ll notice that AHB is a bit complex and touch to operate. While APB takes the simple and straightforward route of operations
  • AHB has a lot of pipelines with which brings forth consequences, while this is not the case in APB
  •  Compared to AHB, you’ll notice that APB uses low bandwidth for control accesses.
  • Yes, APB has the same address and data phase as AHB. But the distinguishing factor is that APB comes with a list of low complexity signals.


As earlier stated, the Advanced High Performing Bus has a lot of characteristics and features. For instance, it has split phases: the addressing phase and the data phase. It also has a clock interface, split operations, one cycle master bus changeover, non-intricate implementations, burst transfer, among other features. It uses one bus master at a single time.

On the other hand, Advanced Peripheral Bus is only required when there is a little latency when it comes to controlling access permits. They are more or less similar to each other, with a few disparities when it comes to some of their features. APB will use a lower signal with its addressing phase and data stage.

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