Difference Between AHB and APB (With Table)

When making comparisons, the AHB employs full-duplex parallel communications, whilst the APB employs huge memory-I/O operations. Chip Bus specifications are used both by the AHB as well as the APB. Waits, faults, and bursts are all possible with the Advanced High-performance Bus. The pipelined ADH primarily links to storage.

AHB vs APB

The difference between AHB and APB is that the former holds for Advanced High-performance Bus, whereas the latter attains for Advanced Peripheral Bus. Whenever it comes to usage, the APB is more straightforward than the AHB. There are also no vacancies in APB compared to AHB.

AHB seems to be a bus protocol that was first proposed in ARM Ltd‘s Advanced Microcontroller Bus Design version 2 publication. Mostly on AHB, a basic transaction consists of just an addressing phase followed by a data phase. A MUX is used to restrict access to a particular device, allowing only one bus master to use it at the moment.

The APB (Advanced Peripheral Bus) is a simple, relatively low, reduced peripheral bus designed for slow electronics. The SoC processors, storage drivers, on-chip storage, and DMA sensors all dangle off the network interface in a typical setup. It is in charge of the processor’s elevated bus links.

Comparison Table Between AHB and APB

Parameters of ComparisonAHBAPB
Stands forAdvanced High-Performance Bus is the abbreviation for AHB.Advanced Peripheral Bus is the abbreviation of APB.
Way of CommunicatingAHB communicates in full-duplex parallel mode always.APB makes extensive use of memory I/O for communication.
Based on UsageIt is slightly more complex and tough to use when compared to its peer.When it comes to operation, the APB is more straightforward than the AHB.
PipeliningThere is a lot of pipelining in the AHB, which might lead to consequences.There’s also no pipelining in APB compared to AHB.
Used forIt is used for both low as well as high bandwidth control accesses.The Advanced Peripheral Bus will only be utilized for limited latency control accesses as contrasted to the Advanced High-performance Bus.

What is AHB?

In AMBA 2.0, the AHB got added as a new feature. It was modified to make elevated designs possible. Split operations, single-cycle bus master changeover, single-clock-edge functioning, and broader data bus setups (64/128 bits) were among the additional features implemented.

From the outside, the lords and vassals and AHB must have several parts. A location and control expander, a scan multiplexer, a writing multiplexer, a decode, as well as an arbitrator are among the elements. The addressing signals (HADDR), the writing data bus (HWDATA), as well as the reading data bus (HWDATA) are all shown (HRDATA). The location is being used to pick a slave, the writing data bus is being used to transmit information from owner to slave, and also the reading data bus is often used to transfer data from servant to masters.

A master should first make a message to the arbiter before seizing ownership of the bus. The arbiter provides access depending on a priority system that guarantees masters with top importance get access first. AMBA has not specified this priority mechanism. Hence it will vary from design to design. 

The route, breadth, and kind of the data flow are all defined by a multitude of signal amplification. The master’s IP message is decoded into slave choose impulses by the AHB decoder. The master receives an HRESP signal from the slave, and also the data transmission between the owner and serf commences.

What is APB?

The APB does not support breaking as just a simple bus. There are two phases in each contract: an addressing cycle (Setup phase) as well as a data cycle (Enable phase). A single clock, PCLK, is used on the bus. PSEL and PWRITE are brought up by the bus during Configure, and the destination is placed upon on PADDR address bus. It puts PENABLE up and puts data on the PWDATA/PRDATA bus inside the Enable condition. On the following clock, the enable indication, PENABLE, gets de-asserted.

The Advanced Microcontroller Bus Architecture (AMBA) protocol team comprises the APB. Time limiters interrupt drivers, UARTs, I/O ports, and other sign-up accessories are commonly utilized. Minimum power usage and interface complexities have been optimized. The APB interface does not use pipelines. Each transmission in APB requires at least two rounds (Setup cycle and Access cycle).

Lower powered peripherals are the focus of the AMBA APB. To enable peripheral operations, AMBA APB has been tuned for low energy consumption and decreased interface complexities. The APB protocol could be used with any iteration of the system bus.

Main Differences Between AHB and APB

  1. Advanced High-Performance Bus is the abbreviation for AHB. On the other hand, Advanced Peripheral Bus is the abbreviation of APB.
  2. AHB communicates in full-duplex parallel mode always, whereas APB makes extensive use of memory I/O for communication.
  3. AHB is slightly more complex and tough to use when compared to its peer. On the other hand, when it comes to operation, the APB is more straightforward than the AHB.
  4. There is a lot of pipelining in the AHB, which might lead to consequences, whereas there’s also no pipelining in APB compared to AHB.
  5. AHB is used for both low as well as high bandwidth control accesses. When compared, The Advanced Peripheral Bus will only be utilized for limited latency control accesses as contrasted to the Advanced High-performance Bus.

Conclusion

AHB has a sharp cutting clock interface, multiple bus masters, split operations, single-cycle bus master changeover, burst transfers, huge bus lengths, and non-tristate implementations, among other characteristics. The transactions in AHB have split into two parts: an addressing phase and a data stage.

Within the context of AHB, just one Bus master is present at any given moment. The Advanced Peripheral Bus will only be utilized for limited latency controlling access requests when contrasted to the Advanced High-performance Bus. The APB, just like AHB, does have an address phase as well as a data phase, but it also features a list of reduced signals.

References

  1. https://d1wqtxts1xzle7.cloudfront.net/51490114/O0701018790.pdf?1485238518=&response-content-disposition=inline%3B+filename%3DDesign_And_Verification_of_AMBA_APB_Prot.pdf&Expires=1623271280&Signature=Jz2ICAKVzQmveWgfRO7i5x7hVnLxHfPfJx9sFjW9YYmv5JEYx6c1sCo-Pdaw3nLr5qVfbdLpvxE1M9cppaTzyJqR0S5O13qwG4XzdqUWrZsJ5WJKuPN7pz2JlI3ym4hwD4UryjpoCi0tPj~iZQMKooMoFY20hbyibUPFfNB9-f4NUbLXAKPgxEySwwZYpJz7LKH9tykDntnFU18uvaEgoFkF5vJasCP~mn6Df5j-d7EIHn5OaqEpx1HvfxVV-yKc~LDHAoaE8IEUJUgLXp9Fd4Z~eVYVT5SOhB3TCZtCaeTv~yrhs1zdR-McSMPxQTmpyqiEfZc0ylMK96NgmdWDvg__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA
  2. https://www.sciencedirect.com/science/article/abs/pii/S1388245713009711
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