What is AHB?
Advanced High-performance Bus (sometimes known as AHB) is an acronym. It is a single-channel bus that is also a shared bus. It has one address channel, one read data channel, and one write data channel, all of which are connected. A simple transaction with AHB requires only two bus cycles, one for the address phase and the other for the data phase. The bus widths at AHB are pretty significant.
Users unable to achieve the timing criteria in AHB will not be able to use the pipeline that registers in their path because the channel will be ignored. Furthermore, because it cannot accommodate the insertion of pipeline registers, it does not allow for a higher frequency but instead restricts the highest frequency that the architecture can achieve.
AHB does not support the Quality of Service (QoS) feature, write strobes or Exclusive support. It only handles transfers that are locked. It has a low power dissipation rating and a low throughput rating. AHB also has predetermined burst lengths, which is a nice feature. In INCR, the burst can last for any amount of time. However, the exact duration is not disclosed.
The ARM limited firm released the AHB protocol in AMBAversion 2, and it quickly became a prevalent protocol until the new version AXI was introduced.
What is AXI?
AXI is an abbreviation for Advanced eXtensible Xtensible Interface. It is a multi-channel bus intended for use in on-chip communication systems. It is a high-performance, high-frequency communication interface that operates in Full-duplex mode. Every channel in AXI is entirely independent of the others, and there is five total. Those channels are as follows: Write address channel (AW), Write data channel (W), Read data channel (R), Read address channel (AR), Write response channel (WR), Write response channel (WR), and Write response channel (B).
Because AXI has five parallel channels flowing simultaneously, many wires are required to build out the layout. A pipeline register can be placed anywhere in the course of any one of the channels by the user, allowing AXI to operate at a higher frequency as a result of this capability.
In addition to unaligned data transfer (using strobes), AXI supports separate address and control phases, byte invariant transactions, burst-based transactions with start addresses issued, Quality of Service, out-of-order transaction completion, Write Data Interleaving (WDI), and atomic operations. AXI contains other signaling systems such as AxRegion and AxUser, described below.
AXI is a burst-based protocol, which implies that it allows for many data transfers for a single request to be processed. When a massive volume of data must be sent from or to addresses that follow a given pattern, it makes the process simpler. This information is known from the beginning, and the lengths of these bursts can range from 1-16 for AXI3 and 1-256 for AXI4.
Difference Between AHB and AXI
- AHB is an abbreviation for Advanced High-performance Bus, a single channel bus with advanced features.
- AHB does not support completing “out of order transactions,” whereas AXI does keep the completion of “out of order transactions.”
- The power dissipation of AHB is minimal, whereas the power dissipation of AXI is considerable.
- The utilization of the AHB Bus is higher when compared to the utilization of the AXI Bus, which consumes 50% more power.
- In contrast to AHB, AXI provides capabilities such as unaligned data transport utilizing strobes and byte invariance, which AHB does not support.
- Write strobes are not supported by AHB, although AXI supports them.
- AHB supports the locked transfer. In the instance of AXI, the AXI 3 supports the locked transfer. However, the AXI4 does not support this feature.
- AHB does not support exclusive transfers. However, they are supported by AXI.
- Compared to the AXIs, the bus latencies of the AHB bus master begin at a lower level.
Comparison Between AHB and AXI
| Parameters of Comparison | AHB | AXI |
| Full form | bus technology that is both advanced and high-performance | Extensible Interface with Advanced Functionality |
| Channel | One channel is available on this bus. | As the name implies, it is a bus with multiple data transmission channels. |
| Features | The early termination of bursts, as well as locked transfers | QoS, Write Data Interleaving, unaligned data transfer, and byte invariance are all features of the XML 1.1 specification. |
| Address space assigned for a single enslaved person | The file size for AHB is 1 KB. | AXI has a file size of 4 kilobytes. |
| Burst Lengths | The AHB has burst lengths 1, 2, 6, and 16 seconds. The INCR kinds are the exception. | AXI3 burst lengths range from 1-16, while AXI4 burst lengths range from 1-256. |