Design of amba based ahb2apb bridge ijcsns international. Apbadvanced peripheral bus bridge, which translates the axi4. Features of ahb2apb bridge the ahb2apb interfaces ahb and apb. As the apb is not pipelined, wait states are added during transfers to and from the apb when the ahb is required to wait for the apb. Ahb2apb bridge is a complex interface between advance high performance bus ahb and advance peripheral bus apb. Amba overview, typical amab based microcontroller, ahb bus. In this case the uut is a core with an apb master interface, this could be the ahb to apb bridge core. Ahbapbsys the components required for an apb system are instantiated in this block.
The adoption of system verilog9 based universal verification methodology7 uvm bridges the gap between. Convention description example courier commands, functions. The veriest amba ahb slave bridge is ideal for ip developers to adapt ip internal busses to the amba ahb bus. Ahb master its a master with the following behaviour. Usually the apb protocol is a slave to the main system bus master, ahb or axi, with a bridge to convert the more complex system bus transfers to the much simpler apb protocol. Apb accesses are of different duration three hclk cycles in the easy for a read, and two cycles for a write. Read and write transfers on the ahb are converted into equivalent transfers on the apb.
Ahb2apb bridge will be communicate between low bandwidth peripheral on apb with high bandwidth arm processors and high speed device on ahb. Is there a limit on the number of apb slaves on the ahb to. Both the ahb and the apb are on chip bus standards. The ahb to apb bridge is an ahb slave, providing an interface between the high speed ahb and the lowpower apb. A bridge is a special node that collapses one or more slave nodes and a master node in a new complex node. They produce the peripheral select signals for each of the apb peripherals. It buffers address, controls and data from the ahb, drives the apb peripherals and return data along with response signal to the ahb 4.
Product specification latency the core is configured for best possible configuration for calculation of read latency. Pdf the 32 bit amba asb apb bridge provides an interface between the advanced system bus asb. Apb bridge the ahb to apb bridge is an ahb slave, providing an interface between the high speed ahb and the lowpower apb. The location of the first ahb apb bridge 0x80000000 in the table above is generally of less importance. There can be n number of finite slaves in an ahb to apb bridge. In amba different bus bridge, protocols such as, asb2apb, ahb2apb and axi to apb can be used.
They also have their width fixed to one word, which means it is not possible to write only an 8bit section of a 32bit apb register. Timing diagrams and more explanation are on the other ahb pages. Though there is a limitation on the number of ahb masters, only 16 masters are supported. Any transactions received on the ahb slave interface are translated into apb transactions on the apb master interface. The axi4 to ahblite bridge translates axi4 transactions into ahblite transactions. Fully parameterised asynchronous ahb3lite to apb bridge. The bidirectional ahb ahb bridge is used to interconnect highspeed and lowspeed amba ahb buses. Using this manual this manual is organized into the following chapters. Advanced microcontroller bus architecture wikipedia.
Ahb example amba system technical reference manual 4. Department of ece sree buddha college of engineering, pattoor. Amba ahb slave to local interface bridge the veriest amba ahb slave bridge design ip offers a simple solution to provide a bridge between the embedded amba ahb bus and a simplified generic local bus. In figure we can see that the uut has an ahb slave and an apb mast er interface. An ahb system definition is made by a representation of the graph topology. Cme ahb2apb bridge design example user guide 1120 capital microelectronics, inc. Design of ahb2apb bridge for efficient utilization of ahb and apb. Apb the apb protocol is not pipelined use it to connect to lowbandwidth peripherals. Methodology7 uvm bridges the gap between highlevel proposition and lowlevel details of the design under verification. Internally, the bridge consists of two unidirectional ahb to ahb bridges and additional logic to. The bridge supports synchronous clocks with any frequency ratio between the two interconnected buses. An apb bus is meant to connect and share several apb peripherals with low bandwidth requirements.
The data travels from a serial bus i2c to parallel bus apb to serial i2c in sync with the respective domain clock. Amba overview, typical amab based microcontroller, ahb bus features, ahb bus transfers. Design amba based ahb to apb bridge using verilog hdl. In the case, emb is the apb slave and the ahb2apb bridge has 2. Ahb pro to show that the ipc apb bridge has completed the apb trade and the data is readied. In addition to previous release, it has the following features. Ahb example amba system technical reference manual. Department of ece sree buddha college of engineering, pattoor pandalam, kerala.
Each of the ahb fabrics m mirrored slave ports is connected to an ahb slave module e. A test methodology is included with the amba specification which provides an infrastructure for modular macrocell test and diagnostic access. Chapter 1 introduction read this chapter for an introduction to the asb example amba system easy. Amba 2 apb specification basic read and write transfers, and the two apb components the apb bridge and the apb slave. Axi to ahb lite bridge cycle model user guide arm limited. To utilize apbctrl in simulations with other components, add apbctrl the use list of your wscript example instantiation.
Axi interface is based on the axi4lite specification 2. Building an apb3 core for smartfusion fpgas 4 figure 4 and figure 5 show the apb3 timing diagrams. Compliance with the amba specification, revision 2. In the example, the ahb2apb bridge module works as slave of ahb bus and master of apb bus, the memories on fpga work as slave of ahb2apb bridge. Here, well quickly go through the different signals. The apb write transfer is then started in the next clock cycle. Read and write transfers on the ahb are converted into corresponding transfers on the apb. External bus interface, memory controller, ahb to apb bridge. Implementing communication bridge between i2c and ahb. This state is needed due to the pipelined structure of ahb transfers, to allow the ahb side of the write transfer to complete so that the write data becomes available on hwdata. Directcore advanced microcontroller bus architecture bus. Interfacing apb to ahb interfacing the amba apb to the ahb is depicted in fig. Ahb lite apb4 bridge the roa logic ahb lite apb4 bridge is a fully parameterized soft ip interconnect bridge between the amba 3 ahb lite v1.
Axi to apb bridge block diagram features of bridge the xilinx axi to apb bridge is a soft ip core with these features. Ahb is a bus protocol introduced in advanced microcontroller bus architecture version 2 published by arm ltd company. The adh, which is pipelined, mainly connects to memories. Converts ahb peripheral transfers to apb transfersthe 16slot apb bridge provides an interface between the highspeed ahb domain and the lowpower apb domain. When talking of the difference between the two, the ahb uses a full duplex parallel communication whereas the apb uses massive memoryio accesses. This ahb multimatrix system contains a flexible power management unit for controlling power sequencing of. Organization purpose of amba ahb or apb protocol descriptions is defined.
Apb clock frequency must be equal or less than ahb clock frequency apb datawidth must be equal or less than ahb data width apb and ahb datawidths must be multiples of bytes. A simple transaction on the ahb consists of an address phase and a subsequent data phase without wait states. This forms a bidirectional interface between i2c supported module and apb supported module. The ahb interface is implemented as a regular ahb lite slave interface, supporting all signals in the amba 3 ahb lite v1. The purpose of this project is to design and verify of amba based ahb to ahp bridge. Apb bridge system on a chip communications protocols. This is the bridge blocks required to connect apb peripherals the highspeed amba ahb bus.
The amba ahb is used to connect highperformance modules and the. This document describes an example that uses the ahb2apb bridge to access the emb on fpga. On the master side, each of the n1 ahb fabrics mirrored master ports is connected to either the output side of an ahb arbiter in the case where each ahb system has multiple bus masters. The proposed architecture is a bridge between i2c master and apb salve. The highlyconfigurable core translates read or write ahb bus transactions to apb bus transactions. An ahb lite bus master connects to the ahb interface of the ahb lite apb4 bridge. Within an apb bus, any peripheral is competing with each other and a transfer can occur when the bus is idle or ready. The apbctrl is a bridge between the ahb and the apb portion of the amba bus system. Where a peripheral does not include this pin, the appropriate input to the apb bridge is tied low. The ahb to apb bridge is an ahb slave, providing an interface between the highspeed ahb and the lowpower apb. In this pdf, published march 2010, pages ii to iv have been replaced, by an edit to the pdf, to include an updated proprietary notice. The bridge functions as a slave on the axi4 interface and as a master on the ahblite interface. Ahb signals the ahb specification defines a list of signals and defines how the different blocks in the system use those signals to communicate.
Integrated circuits have entered the era of systemonachip soc, which refers to integrating all components. So, if there is no apb bus provided, the apb slave blocks can be connected to ahb masters through the ahb2apb bridge. The ahb2apb bridge ip supports the following features. This book is written for hardware and software engineers who want. Some legacy software may assume that the bridge is located at the specified. Axi4 to ahblite bridge block diagram is shown in figure 11 and described in following sections. Parameterised asynchronous ahb3lite to apb4 bridge. With the progress in technology, tools and methodologies need to be improved to meet the challenges of transforming verification environment. The remainder of the pdf is the original published pdf. Apb clock speeds can typically be tuned down from the ahb speed using configurable clock dividers. Ahb to apb bus bridge the ahb2apb implements an amba ahb to an amba apb bus bridge, allowing the connection of peripherals with an apb interface to an ahb bus. Ahb example amba system technical reference manual ahb.
The bridge functions as a slave on the axi4lite interface and as a master on the apb interface. Apb interface is based on the apb3 specification, supports optional apb4 selection 3. The intent of this paper is to throw light into benefits associated with ahb2apb verification using universal verification. The axi4lite to apb bridge block diagram is shown in figure1 figure1.
For more information on the apb bus, see the amba specification. This example shows how to instantiate the module apbctrl. Department of electronics and communication engineering, mit, manipal contd. The ahb2apb interface is designed to operate when ahb and apb clocks have the any combination of frequency and phase theahb2apb. The bridge appears as a slave on ahb, whereas on apb, it is the master. The ahb lite apb4 bridge natively supports a single peripheral, however multiple apb4 peripherals may be connected to a single bridge by including supporting multiplexer. Axi2apb bridge verilog code cortex r4 axi2apb bridge isc307 axi2apb verilog code for ahb bus matrix amba axi to ahb bus bridge verilog code axi to apb bridge axi bridge. Ahb to apb bridge the ahb to apb bridge interface is an ahb slave. A full ahb or ahb lite master, such a microprocessor, can connect to its ahb. Pdf design and implementation of amba asb apb bridge.
As the apb is not pipelined, then wait states are added during transfers to and from the apb when the ahb is required to wait for the apb. When accessed in normal operation or system test it initiates an access to the apb. Interface apb to ahb the exchange starts on the ahb at time t1 and the address is investigated by the apb interface at t2. The advanced highperformance bus is capable of waits, errors and bursts.
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