AHB is an example of a point-to-point read bus, in contrast with older bus architectures that use a single shared data bus where each slave accesses the bus via a. office-com.us › documentation › ddi The Advanced microcontroller bus architecture (AMBA) protocol is an open standard, on-chip bus specification that details a strategy for the interconnection and.
Ahb bus -
Any other peripheral in the system could also be included as an AHB slave. Only one bus master is allowed to actively use the bus at any time. AHB slave A bus slave responds to a write or read operation within a given address-space range.
The bus slave signals back to the active master the success, failure or waiting of the data transfer. AHB arbiter The bus arbiter ensures that only one master at a time is allowed to initiate data transfers.
An AHB would include only one arbiter, although this would be trivial in single bus master systems. AHB decoder The AHB decoder is used to decode the address of each transfer and provide a select signal for the slave that is involved in the transfer. A single centralized decoder is required in all AHB Implementations. A central decoder is also required to control the read data and response signal multiplexer, which selects the appropriate signals from the slave that is involved in the transfer.
Figure Multiplexer interconnection Design analysis: Basic transfer: An AHB transfer consists of two distinct sections: The address phase, which lasts only a single cycle The data phase, which may require several cycles. Figure Simple transfer In a simple transfer with no wait states: The master drives the address and control signals onto the bus after the rising edge of HCLK. The slave then samples the address and control information on the next rising edge of the clock.
After the slave has sampled the address and control it can start to drive the appropriate response and this is sampled by the bus master on the third rising edge of the clock.
Transfer with wait states: The address phase of any transfer occurs during the data phase of previous transfer. This overlapping of address and data is fundamental to the pipelined nature of the bus and allows for high performance operation, while still providing adequate time for slave to provide the response to a transfer.
A slave may insert wait states in to any transfer as shown in the figure 3. Figure Transfer with wait states For write operations the bus master will hold the data stable throughout the extended cycles. For read transfers the slave does not have to provide valid data until the transfer is about to complete. When a transfer is extended in this way it will have the side- effect of extending the address phase of the following transfer.
This is illustrated in figure 3. Figure -3 Multiple transfers In figure 3. Both incrementing and wrapping bursts are supported in the protocol: Incrementing bursts access sequential locations and the address of each transfer in the burst is just an increment of the previous address. For wrapping bursts, if the start address of the transfer is not aligned to the total number of bytes in the burst size x beats then the address of the transfers in the burst will wrap when the boundary is reached.
Figure AHB bus master interface diagram 3. Figure 3. The slave uses HSELx select signal from the decoder to determine when it should respond to a bus transfer. All other signals required for the transfer, such as the address and control information, will be generated by bus master.
AHB Decoder: The decoder in an AMBA system is used to perform a centralized address decoding function, which improves the portability of peripherals, by making them independent of the system memory map. Each master also generates an HCLOCKx signal which is used to indicate that the master requires exclusive access to the bus.
The detail of the priority scheme is not specified and defined for each application. Protocol Checker: HPChecker is a rule-based protocol checker, thus how to establish a set of well-defined rules is very important. Besides, according to our design experiences, we add new rules to increase our error finding ability.
In conclusion, our protocol checker has rules, including master-related rules, slave-related rules, reset-related rules, and bus components- related rules. Bus components include arbiter and decoder. Protocol checker is the main core of HP Checker, the inputs are all AHB bus signals, and the outputs are error signals and corresponding master and slave IDs. Error Reference Table ERT : Traditional protocol checkers will assert error signals or a printout error message for every error occurs,but this way is very inefficiently for early debugging in long simulation period.
In early debugging period, there may have many errors, especially when test bench or real case application ahs very long execution time. Such large amount of log messages or error signals waveform could help designer to debug limitedly, because that will be hard to read or analyze. Moreover, we do not care about the timing information when error occurred in most case. Thus we provide error reference table that can summarize what errors have been occurred.
Ahb bus -
The AHB is the backbone of the system and is designed specifically for high performance, high-frequency components. This includes the connections of processors, on-chip memories, and memory interfaces among others.
Figure 1. It was added to accommodate high-performance designs. Some of the new features added were split transactions, single-cycle bus master handover, single-clock-edge operation, and wider data bus configurations, i. An AHB must contain a number of components outside of the masters and slaves. These components are an address and control multiplexer, a read multiplexer, a write multiplexer, a decoder, and an arbiter. Figure 2 shows three masters connected to four slaves on an AHB.
The address is used for slave selection, the write data bus is used to move data from master to slave, and the read data bus is for moving data between slave and master. Figure 2. The arbiter grants access based on a prioritization scheme that ensures masters with a higher priority are given access first. This prioritization scheme is not defined by AMBA and will differ between designs. A number of control signals are used to define the direction, width, and type of the data transfer.
The AHB decoder receives the address signal from the master and decodes it into slave select signals. The slave responds to the master via an HRESP signal and the data transfer between master and slave begins. In total, there are about 20 different AHB signals each with a unique purpose. Many of the same signals on an AHB are used for the ASB aside from certain control signals that allow for split transactions.
The operation of the ASB starts with a master requesting access to the bus from the arbiter. The arbiter grants the request and the transfer begins. The decoder decodes the address placed on the bus and selects a slave. The slave responds back to the master and the data transfer takes place.
Figure 3. Revision 2 simplified the bus further by having all signal transitions synchronized to the clock's rising edge. Thus, the bridge is the interface between the high-performance bus and the low-frequency peripherals. The peripheral devices on the APB are the slaves. Figure 4 lists the APB signal names. Figure 4. Figure 5. Example of an AMBA system.
Click to enlarge. This system has been simplified with some signals and minor elements such as reset signals and multiplexers removed. Output signals leave the right side of a block, and input signals enter the left side of a block. Input signals are also denoted by an arrowhead. Thicker lines represent larger data paths.
This system is performing a write to one of the APB slaves over the course of about seven clock cycles. The AHB is a pipelined bus and has dedicated read and write paths, so a read could happen partway through this write. AMBA revision 3. Instead of a system bus, the AXI interconnect allows transactions between masters and slaves using only a few well-defined interfaces.
Figure 6. AMBA is an open standard that outlines how components on an SoC can exchange data in a fast and efficient manner. AMBA has become a de facto standard and is currently on its 5th revision. Starting with revision 2. While much of these bus protocols have been supplanted by future revisions of AMBA, they remain relevant in legacy designs and as a foundation for future learning.
Related Content.The address is used for slave selection, the write data bus is used to move data from master to slave, ahb bus the read data bus is for moving data between slave and master. Ahb bus incrementing and wrapping bursts are supported in the protocol: Incrementing bursts access sequential locations and the address of each transfer in the burst is just an increment of the previous address. Such large amount of log messages or error signals waveform could help designer to debug limitedly, because that will be hard to read or analyze. Thus we provide ahb bus reference table that can summarize what errors have been occurred. Access to the target device is controlled through a MUX non-tristatethereby admitting bus-access to one bus-master at a time. Figure 2.